So, just xeno-slaves everywhere? Since research is done by mostly disassembling stuff, creds might be sufficient. But why would one need so much influence if colonization is not a priority, most aliens are enslaved outright == no alliance/treaty drain? Just for edicts? But really, it doesn't matter much for slaves.
Xeno-slaves as far as the eye can see, produce credits from your homeworld, and he isn't even going to unlock colonization in the first place. He doesn't care as much for your minerals as you might think, either (he's already getting plenty, his pops have Very Strong/Industrialist and he'll have his policies, edicts, and governors optimized for this). He's mostly enslaving your pops to control their Happiness malus and manage Factions.
Screw research, he only needs a handful of techs and will get most of the Militarist techs he needs from debris/space monsters (he basically only needs rank 2 kinetics and crystal-forged armor, anyway, his idea of "late game" is about thirty minutes into the match).
He won't be allying with anyone or making any treaties whatsoever, he'll be rivaling everyone he meets instantly and pumping influence to cycle admirals as fast possible to get optimal stats, then he'll optimize his scientists, and governors, in that order.
In many ways it's not slavery that's OP, it's hands-on micromanagement and unbridled aggression (...and in and of itself, that's not a bad thing. imo it's corvettes that need the nerf, not slavery, sector a.i. needs a buff/change that makes using slaves easier for those
aren't kinda-maybe-partially-OCD-micro-nerds like myself and probably Tuk, too, though I don't mean it in a bad way and I'm not saying he has OCD. Guys like us who get into optimal builds and start orders, well, we're just gonna move on to "the next OP thing" anyway, so it doesn't really even matter that much what you nerf, it only matters how fast we can crowdsource ways to exploit the new meta).
* P.S. BTW, I did slave-rush long enough to get a pretty good handle on how it works and how to beat it (pro tip, fix their position and wipe them out or vassalize them before they take their third planet or you've already lost, you just don't know it yet), I've since moved on to builds that make me more acceptable to both human and AI allies, but other than the slaving part I play pretty much exactly the way Tuk describes, though I abuse armies and abandon planet where he is abusing Faction mechanics, and my goal is to make you my willing servant, not to remove you from the game entirely. This is all because I like longer games now and a human vassal that's gonna auto-win when you win (and not doing silly stuff like trying to call a FE down on your head because they hate you IRL now) is 10x better than an AI vassal or even another homeworld, they can help with tah uber micro needed to pull off the really fun large-scale coordinated assaults the game allows for, and I prefer human vassals to alliances/feds early game because the vassals don't preclude me from joining alliances as I need to, whereas once I'm in a federation I'm kinda stuck there for political reasons unless I'm the one who started it (a Federation I start is going to last exactly 9 years every time, lol, then I'm going to invite everyone to the "new" one..).