I've been writing up some ideas for how the Empire Maleficium managed their sphere of influence, since I've come to realize they'd have to be extremely strict in that regard. Given that several smaller alien governments will exist inside, I tried deciding on their policies regarding them.
That's not important, though.
What is important is that I developed an interesting idea that I feel everyone should be exposed to.
"Free colonies" are worlds which contain a population of a species but do not hail to the main government for that species. I expect that many of the people who participate here and found their own spheres will expect a certain degree more unity within theirs than the Terran Sphere. This is to be expected; people like having their government and species be tied together and unique.
But, given how large our empires are and how hard they could be to maintain, some worlds or parts of the population are bound to "slip through the cracks", so to speak.
Thus, "Free colonies". This allows for some degree of species and cultural integration, ala Star Wars, rather than the classical "my nation only has members of my species in it and doesn't share any technology".
I encourage everyone to explore the possibility of their species having such worlds. The Empire Maleficium keeps a very close eye on immigration and colonization, but sometimes worlds lose contact with the Empire and are cut off. Sometimes "covert colonies" are formed by an alien nation smuggling intimus onto another world without Empire control and oversight.
What about your nations? How many of their explorers have become stranded far away from home, left to found their own nations? How many have fled to other Spheres seeking a different way of life?