Great game! A few of my suggestions are as follows:
1. Espionage spending could be further sub-divided into smaller categories to micro-manage based on your goals: (i) using "agents" to steal technology (technology win); (ii) using "moles" to gather useful information (it would be useful, for example, to know when your enemy is beginning to build up an army against you) (combat win); and (iii) using "propaganda" to weaken the approval rating of your enemy’s population (or gain influence points). Espionage spending, right now, seems a little bit ineffectual compared with other types of spending.
2. An orbiting spacecraft should not be able to impede a planetary invasion, unless the orbiting spacecraft has at least one weapon. It does not make sense to me that a scout could realistically serve as a buffer against a planetary invasion?
3. What about borrowing money from other civilizations or galactic banking guilds? You would pay interest, as with buying ships on credit. As for collateral, you could either secure the loans with ships or technology. Anyone reminded of mortgaging properties in Monopoly? If you do not pay timely, the lender could foreclose on the collateral (and use it against you). (Securing loans with planetary improvements is senseless because they are fixtures rather than movable property.) You could also lend money to alien civilizations at war with other civilizations (a great way to divide-and-conquer while remaining neutral).
