I know that the odds of this happening in a new supplement are slim to none, but if one or more new 'Major' Races were introduced, what kind of civilization and type would you like to see? Is there a niche open in the Third Imperium setting that would be a good fit for a new Major power, so it wouldn't feel redundant?
I think a heavily roboticized or cybernetic-reliant civilization could work. For example, in the couple of non-TI games I ran years ago, I had a human-variant polity known as the Mechus Empire. Several disasters forced an exodus fleet to heavily innovate their AI. They succeeded tremendously and grew to be one of the most powerful factions in human territory. The human population remained small and either retired to live luxuriously on carefully tended and heavily defended garden worlds or uploaded their consciousnesses into a VR network designed to be a paradise. Their robotic servitors' purpose is to maintain their beloved masters' standard of living, and if that means being an expansionist power exploiting lesser human or alien polities, so be it.
For the Third Imperium, the founding humans of the Mechus Empire could simply be another Ancient transplanted branch of Humaniti, though them being human is not an important part of their backstory.
When researching 2300 AD recently, I ran across mention by one or two Referees liking to introduce the Kaefer into Charted Space. The Pentapods also seem to be a good choice, IMHO. Any opinions on this?
Does anyone have any homebrewed Major Races, or experiences with games introducing them, they'd like to share?