Alright i just had an idea. What about every colony in your empire when you research star federation every planet has it's own election. Different parties control different planets and the way i see it this can have good and bad effects on your empire.

Good ponits:
- The bonuses can apply to different planets, so it can put a different spin on wars and the stragies used to exploit weaknesses.
- Depending on the state of the empire with poltic's can change (eg if the wars going well, increase in war party popularity on frontire planets decrese in homeworld and other planets futher to the border)
- Politial/Ethical desions have to be made (eg The industriusts think that the newly colenised planet [name of planet] is struggling to get up to speed and argue that a strong indusual sector can recover the planet from it's lack of prosparity. Choose a)give them full governing powers (but no sucssun of course)+20% on both indus. and military rating - all the bonus you get from the defult goverment b)give them certain rights but dont let them full office power +10% indus. and military - half of all the bonuses of the defult goverment or c)no power, our people should be loyal to the empire and working of it's goverment -+ no change)
- Planets of a the same goverment have better esponage on each other or the faction of your goverment give you bonuses on esponage on empires with the same goverment as the faction of your empire
- Planets of a different goverment within in the same system give influce ponits in the election of the goverment majority (this can also apply to planets that different planet is trading with)

Bad ponits:
- Might be tricky with 100 planets (possable solution: have an empire vote or choose planets that should have individual voteing and then have the remaining planets do a empire vote or have every planet have a individual vote)
- You could have a system that when a cluster of planets have the same methoed of goverment (different to the empire's goverment) they can decare there independance and become a minor race and if reverts back to the goverment of the empire it becomes part of the empire agian
- If you declare war with a empire every one of the planets with the goverments that corosponds with your eniemes they join your enemy, every planet that your enemy has that has a goverment the same as your defult goverment, join you.

If you cant intergrate it in, I understand it's a bit tricky.