First of this is a copy of my steam thread:
http://steamcommunity.com/app/273070/discussions/0/558754259822654555/The main problem is: To form a Federation two factions are needed.
These two faction are allied and help one another.
If they do good they can dominate the galaxy together.
If they do bad they both get wiped out.
I cant think of a reasonable scenario how you can kill off one alliance member without the other one falling shortly after.
I know many people try to figure out how to keep all races alive, but I wanted to try to get the achievements and donĀ“t know how to get them.
This whole concept is only a problem if my understanding of "you win if all races alive are part of the federation" is correct. Otherwise a big fear empire might work.