There are only a few things I have to mention with regards to this.
First: Ground invasion where I have to kill everybody on the planet seems a bit extreme, I noticed that you guys made a point of making the AI wise enough that it knows when it's beat. What if that's extended to planetary invasions, lets say the planet I'm invading starts out with a five to one advantage, by the time we're roughly even in troops it should know that it's beat, then maybe it surrenders.
Second: Seing as how I can do information warfare and capture planets culturally I can already get aliens to become part of my empire, so following from the earlier possibilty of the remaining populace of a world surrendering then you get three options, like an event. 'You've got POW's what do you want to do with them?' For the record I kind of think that once you get Xeno Ethics and have chosen an ethical stance you should be locked into your decision on any event.
Anyway, to my POW scenario you get your three options:
Good- You abosorb them into the new population of this planet.(Approval - , Population+, Tax income +, Monetary bonus)And your soldiers kind of ransacked the homes of their dead comrades for valuables. Alternatively you could try and repatriate them for an influnce/diplomacy bonus, I didn't think that would be too helpful.
Neutral- Execute them, who needs a bunch of lazy Torians on my newly conquered Drengin world?(Monetary bonus) We like to loot.
Evil- Labor camps! Extra production, the production bonus will gradually decrease as the prisoners die,but maybe you can whip those punks to help them produce that brand new frigate you so deperately need. (Still a monetary bonus) We still like to loot.
Note- You may consider evil and neutral interchangeable, but in my opinion execution is more in the way of a coldly rational ambivalent neutral race.
