If I were to start a game with 6 player races and make 5 of them neutral races (no installations, etc. ), would that cause any significant issues (such as slowdown) later in the game? Furthermore, if I could build up a sufficient military force and occupy those neutral nations, could I later add their population to my own without incident?
Essentially, I want to model a mostly intact population of earth while operating with only a portion of that population, to maintain game balance, RPing the other races as fellow megastates without the capability or motivation for interstellar expansion. Would this be possible, or would I be better off creating my primary player race and a single other neutral player race titled something like "Unaffiliated Nations"?