Likewise making a change, although much smaller. Same xeno-race, tech, societal organization, and aesthetic, with the modest change of being well-established as loyalists, running a more or less autonomous client state with firm allegiance and love for (some/most?) Imperial institutions. Considering the heavy Darwinist philospohical slant and the preexistence of a selective and cooperative caste system, peaceable amalgamation into the conquering Empire is more or less plausible as a matter of both pragmatic acclamation and genuine acceptance of the right of the conqueror who could be doing far worse, silencing the usual grumblings and chafings you find in other xeno and techno-barbarian subjects. Chief value to the Empire was probably in military lease and fissile & fusion weapon manufacture, often both at once, since much of the weapons aren't terribly practical for other species to use or adapt. Less lizard Imperial Japan-Ummayads, more xeno-Byzantine Armenia, or maybe the Britons.