Usually I play "good guys" empires but all those species rights options made me wishing to go full 1984 and build not even totalitarian regime, but elaborate sadistic totalitarian regime which torments all its inhabitans (including elite) in complicated ways.
Forced resettlements to horrible worlds, lowering happiness for permanent unrest, working to death, various kinds of slaves, making food out of aliens, elaborate and random genocides, sterilization, robots, mind control, clones, wars, armies, roleplaying and sending leaders to death, planned starvation, bombardment, tormenting natives and presentients, diplomatic betrayals, propaganda, poverty, forced terraforming of species homeworlds to horrible climates, persecution, assasination, inviting immigrants and then exterminating them...
Then do a story of it and call it "2284" or something like that
It would be even better if future expansion introduced weapons of mass destruction, more diplomatic options, environmental pollution etc
Figuring out how to reach the highest possible misery to galactic life without empire breaking down