Part of the problem with opening up the different government types is that the NES is designed around the concept of a noble dynasty. If someone can come up with a good story as to why a Democracy has a somewhat hereditary leader, I'm all for it. Even if you play as an important family within a republic, I'll allow it. But that's the purpose of the NES, which is why each individual had their own stats. Where I'd love to have you along, I'm not going to change the system if that's not the sort of game you're interested in.
That said, I understand your concern, and thank you for just telling me what you want. My intention with designing the aliens was to create something that allows players to make something different. Put their own twist on it, create their own culture within the broad term "Terthen". But by creating the aliens, I guess I already created too many limitations.
But there's the problem. How do you create a broad culture, that allows very little limitations, but is still relatable? Do you just give them the anatomy of the aliens, and give no backstory? Rewrite their history? Allow players to create their own, somehow genetically-related races? Just give up on including aliens?
That's why I'm leaning to making the Terthen more tribal. "Tribal" is a very broad term, but still easily relatable to human society. Think of the Steppe Hordes, or alternatively the Native Americans, or whatever else you want. There seems to be some interest in these new Terthen. But quite frankly, I don't know what option is best. Which is why I'm petitioning to the players so much. Sorry guys, but I'm still figuring this all out.