First off, great game, I bought it the day you guys did the release and have been very happy with it.
I read through a couple pages of these user-recommended tweaks but since I am at work, going through all 11 pages was a bit much, so I apologize if this has already been mentioned:
1) On the planet-production screen where the various planet improvements, super projects & trade items are listed, it would be nice if right at the top of the list of this stuff, much like in the ship design menus, there were 3 tabs that said 'Planet Improvements', 'Super Projects', and 'Trade Items'. When none are selected, all the improvements and such are displayed, but when they are selected individually, the appropriate items show up. This would be useful since often when I am checking which planets have what, if I have gotten behind the construction of super projects & trade items, the list gets somewhat overly long and its a pain to keep scrolling the list to add the basic planet improvements.
3) Spying-improvement research (gain +x% per level of research)
3) Negative racial attributes; I am repeating what another poster has said as well, I think it would be a good idea to allow players to select negative racial attributes to gain points they could put in other attributes, with a maximum number of negative points allowed. The only issue is that this would likely force SD to rebalance the AI races.
4) Make a hotkey for going through owned planets in the planet-construction screen, instead of having to hit the previous/next buttons at the top
5) Hotkey for scrolling through 'inactive' ships, ie ships that have no orders such as freighters who arrived at their destination after all the trade-slots are filled.
6) Events log of events, includes planets being taken over via influence, freighters arriving at destinations, being attacked, etc. Its too easy to quickly click the 'ok' button of these event notifiers without seeing where they happened.
7) Playing the campaign and changing the default player stats should not alter the human SD-made race. This is kind of stupid really since theres no way to reset the Human race abilities to their defaults so after I played the campaign, I had to 'make up' new abilities for the humans which was annoying since their settings should not have been altered in the first place. The campaign player race should be its own thing that does not alter anything except perhaps the custom-race slot. This is a must-have, not optional.
8) Custom AI Race Creation, players should be able to create custom races they can play against (ala Space Empires IV) via the same interface they create their own race with, then save it and load it up as an opponent-controlled race in the non-campaign gamemode. Since the AI plays based on its abilities and this is already being done when the player alters the humans in the campaign mode (see recommendation #7) , this should not be difficult.
9) Ship creation screen, this DEFINITELY needs a filter system for the stuff already on the ship. Its really annoying to spend 15 - 20 minutes designing a ship with a lot of asthetic pieces and then when editing the actual equipment like engines, weapons, etc, having to scroll through a long ass list of asthetic objects you've put on it. Just use the same filters as are already on the top of the creation-menu, Visuals, Weapons, Engines, Defense, Modules. This would make the ship-creation screen perfect imo.
10) Ability to mass-upgrade ships such as fleets
Final Note on Spying:
I have noticed that GC2 relegates spies to the sidelines as a passive force in the game, and while I can understand the fustration of players who are undermined by AI spying, I think this really adds a more complex, better element to the game. While not a tweak, I implore the GalCiv2 developers to make spying a more integral part of the game strategy. This includes spending money on counter-intelligence and offensive spying operations against other races which also carries the threat of being discovered and attacked in turn. Perhaps have a toggle where players could say whether or not they want to play with the advanced spying rules when they start a new game. Not an ideal solution, but I'd really like to see more spy-strategy in the game.