First of all I am a fan of the series, having complete edition for 2 and 3, so thank you for making another one, it looks promising.
I do have some suggestion for hopefully improving the population and planet management systems.
I would recommend changing population bonus from percentage to a base value to sectors, manufacturing, farming, wealth, influence and science. This is because population not situated on your core worlds doesn't seem to contribute much to your empire - in fact I was annoyed in my play trough that they seem to require food for seemingly very little return. I just wanted the planets base values and ideally only one population. With it being a base value addition to colonies, this will allow their contribution to be transferred to the core world managing the colony using the existing system. I think this will greatly enhance the value of population count in your colonies, making planet population more of a factor also for colonies and not just core worlds. I also feel that population adds to little at this stage balance wise and changing it so they add to the base values will allow them more easily contribute in a meaningful way on their own.
Secondly, while I like the population skills (Intelligence, social, diligence and resolve) for leaders, I dislike it for population. My reason for that is that it adds a lot of micromanagement to handle efficiently and it is less of a player choice and more of a micromanagement activity. Especially if you want to move people around since it mostly affects core worlds where you can specialize your population. So I like it for leaders because there it gives you tangible choices and tradeoff without adding a lot of micromanagement, but for individual population it seems to be more of a hassle to the player than player choices and engagement. Sending all the population with high expectation to become star bases and such isn't a rewarding experience, outside the first few times, when you get satisfaction from abusing the system and sending anyone in your empire that complains to the starbase gulages (I am assuming that high expectation affect morale). Alternatively I think there must be an automation system to handle the micromanagement for you. Say you could set an immigration policy on all planets. This planet wants high intelligence followed by manufacturing, and expectations less than 7 and gradually the population would shift itself around in your empire doing the micromanagement for you while leaving the decision making to you. There could also be technology, executive orders and planet project to speed up this migration. However I think this will be unnecessarily complicated, with very little reward for the player overall. Also from what I have heard developers of Stellaris (another 4x game) say in interviews it is also a potential performance pitfall.
Thirdly, specialization. I would let population give a bonus to all sectors except morale perhaps, and then let the specialization (scientist, farmer and so on) add on top of that. I think this will give more incentive to specialize the population and make it a more interesting player choice. I would also suggest adding a neutral specialization that adds too all sectors and dual specializations, say for instance Engineer adds to manufacturing, Development Engineer adds to both manufacturing and science, ecological scientist adds to science and farming (or reduces pollution maybe), Jack of all trades adds to all. This allows for a layered reward system, where the neutral specialization add the most, but it is evenly divided so harder to amplify with building bonuses, Single specializations that adds to only one sector, but adds the least as a result since it is easier to amplify and dual specializations witch sits between neutral specializations and neutral specializations. It will also be possible with gradual upgrades, making you invest resources over time into your population making them an increasingly valuable asset of your empire as your tech progresses. It also feels kind of arbitrary to specialize population at core world and not on colonies. Particularly since population on the colony ship has a specialization. It would be nice if there was a simple system to specialize that part of your population too. I also think that specialization should be planet wide improvement to reduce micromanagement and since most planet would ideally want the same specialization outside of micromanage population skills (Intelligence, social, diligence and resolve). With such a change I would also suggest making population specialization a separate tech branch, with the common options being joint together in tiered upgrade. This also open up for the possibility of adding exotic sub branches with more exotic specializations both at launch and during future DLCs.
Fourthly, Colony upgrades. It feels a bit weird to colonize planets and then spend no further resources on them at all, leaving them completely undeveloped. Don't get me wrong, I absolutely love the idea with core world and then have colonies that you don't need to manage manually. Absolutely a stroke of genius to have it that way, I love it. But at the same time it feels a bit weird from a story / empire perspective, it feels a bit disconnected from the experience even tough it improves management so much it is absolutely bliss to play compared to previous editions. What I would suggest trying is to implement a simple upgrade system, with the upgrade projects selected and done from the corresponding core world (but viewable from the colony itself). Selecting the colony from the core world management screen ( I also think here would be a good place to allow for the specialization of that colonies population, preferably planet wide specialization) seeing the relevant data and upgrade paths. What I am envisioning is a colony leveling system, where you can select each colony from the corresponding core world management screen, see the colonies level and level it up with a project. Leveling up will increase the base values by a percentage of the original values. So for example a colony with 2 production and 1 science at level 1 might have 3 production and 1.5 science at level 2. Colony level should also increase morale on the planet as it gets more developed along with making it more influential and harder to culture flip. I think the challenge is to preserve the simple management that you have achieved with the vastly improved system, but still retain a little bit of player choice and development of the colonies from a unified screen in the core world.
Fifthly, I would like you to consider if making population a part of the planet and ships a benefit instead of being its own entity, in conjunction with the over mentioned suggestion. I think that having population be a part of the planet would provide a clearer interface to the player. With trait such as collectivist, Individualist and such being planetary population values. When a pop is transferred to a colony ship it keeps the same percentages. I think this will be clearer to read on the colony management screen, easier to balance and track during development and easier to create game mechanics that interact and influence this in a clear and meaningful way. It is also potentially a performance benefit. If population are implemented as struct/classes, then there is potentially a lot of objects in memory, witch also could lead to less than ideal memory usage or memory locality. Taking the struct/class in as a fixed sized field for colony ship and planets could make for less objects, less memory usage and or memory fragmentation. Making it easier to create a single coherent array in memory of all planets on map without wasting a lot of memory or having memory indirection for population. I know from the interviews of the developers of Stellaris (another 4x game) that population can be a significant performance contributor.
Sixthly, I would like an option on colonies to override witch core world they belong to. This is useful if two core worlds are similar distance away from the colony, but are specialized differently.
Seventhly, I would like to have shipyards that can have multiple sponsors such as in the old games. This is useful if you have two or more core world close to each other.
Eightly, I would like you to consider non tile upgrades of core worlds. This would be planet wide modifier or sector wide (core world plus all the colonies under its management). It is interesting because it isn't bound by the tile system and the adjacency optimization choices. Restricted by a different set of restrictions than the tile system, complementing the existing excellent and proven tile system. For instance the number of colonies + core world under management could determine max upgrade count. Core world should count as more than one in such a case I believe, and perhaps colony levels could be a factor if that suggestion is implemented. Or perhaps the total population under management or the total sector size adding all planet sizes under management together. It could also be a fixed size for all core worlds regardless of planet size, that could be further expanded with tech, I think this perhaps is the best options, because having upgrade slots that depends on the entire sector (core world + colonies under management) will either be very interesting during warfare and culture flips or an absolute management nightmare (think nightmare is perhaps the most likely outcome). I think having improvements that are independent of tiles will open up for a greater variety of upgrades and the player choices available, especially if they can be sector wide or just for the core world and the ability to reassign witch core world a colony is managed from is implemented. Giving players the options of creating core world that have none or few colonies under its management relying on the combination of tiles and these new upgrade slots to create a new interesting type of planet strategy offering new player choices and options. While also allowing the creation of massive sectors favoring sector development over core world development. To keep it balanced, maintenance could potentially be scaled based on planets affected. I also think this opens up for more flair, distinction and grandeur to your empire, deepening the story of your empire and play trough. It also open up for excellent additions in future DLCs.
A few potential examples.
Hypergate network - reduces or remove decay from all colonies under this core worlds management
Sector research collaboration - increases science of all colonies under management by 10%/20%/30% or 1,2,3 (Tiered upgrade)
Sector manufacturing collaboration - increases manufacturing of all colonies under management by 10%/20%/30% or 1,2,3 (Tiered upgrade)
Drone defense network - All planets in sector (core world + colonies) are defended by drones. Number of drones depend on upgrade tier.
Sector wide entertainment - All planets in sector (core world + colonies) have their morale increased
Unified governance - The governor bonuses is added to all colonies under management. Percentage bonuses added to each colonies output before it is sent back to the core world so the added benefit is affected by the decay.
Tau satellite research and observatory constellation - adds 2 science to the core world
The world cracker - On the core world, halves maximum population, removes farming value and adds pollution, but gives a dramatic increase in production
Death trap (Military outpost) - Removes farming, science wealth, halves manufacturing and set morale to 100. Also makes the planet immune to culture flips, the planet always are in its owners culture zone.
Science fabricators - takes all the social production and adds it to science instead. Removes all manufacturing buildings.
Farming fabricators - takes all the social production and adds it to farming instead. Removes all manufacturing buildings.
Distributed shipbuilding - Increases shipbuilding speed in the sector (military production)
Ecumenopolis - Increases max population massively and reduces population impact on morale. This should perhaps also affect the tile system and its effect based on planet size. I envision it also placing restrictions on farming and manufacturing. Being a world suited for influence, science and wealth, but not farming and manufacturing.
Thank you for making an excellent game and listening to my lengthy feedback.
Keep up the good work
Andreas / happy customer