I was fortunate enough to have a research federation form, and joined that. I wanted to join the "Common Ground" cluster I started near, even shared ethics... but they preferred to rival me, fair enough. The research federation is as underwhelming as I'd heard, I just found it appropriate for my Mechanist run.
Like- research treaties are pretty useless, generally? Giving them some multipliers doesn't really help. It certainly doesn't help *me*, but I suppose letting them crib off my notes strengthens the galaxy. Replacing "+25% damage to crisis" with "+20% research speed during crisis" is horrible though, 200 years in I'm already on tier 10 repeating techs and the crisis is probably decades away. I haven't even reached the capstone of, wowzers, +1 megastructure build capacity (megastructures you can build at one time) which I thought would be nice, but with Master Builders and the Ascension edict I'm already at 3 - which is all I need, I'm wrapping up. I suppose it would let me build more ringworlds faster but I don't *need* ringworlds as ascended synths. The alloys are better spent making mining-habitats to feed my 4 ecumenolopi. (something tells me I've won this game)
The research federation has also been surprisingly resistant to all my votes, and I can't dominate them all because I played tall and generous. Which is fun and democratic, I don't particularly mind... I just wish they let me form the federation fleet before 200-years-in. And it's only minimal contribution, because research federations have weakened fleet laws. Even without the fleet, we managed to absorb basically the whole galaxy through vassalization or outright war (I left the declarations up to my allies, but assisted with my fleet as necessary). The first khan got poisoned after a handful of years, and wasn't a threat anyway. I could have made the second khan a protectorate but they got eaten by my allies instead.
The odd result is that we have literally every ethic in the federation (there's a cheevo apparently) and that hurts a lot in non-Union federations. With all 7-8 of my envoys dedicated we only gain about 3 cohesion a month, and it drops every time we vassalize something. This means that we haven't hit the final level yet 200 years in. Not that the rewards are great.
I guess I'm satisfied fluff-wise... no, I'm actually disappointed there too, because shouldn't this have turned the galaxy materialist? Maybe even a bit egalitarian? But nope. There's definitely a materialist draw from the automatic research pacts, but spiritualist ethics are *absurdly* hard to change. Much like egalitarian ethics as a friend of mine pointed out (but I *like* that so it's *different*). I just wanted to pass the research proposition which allows robots to exist - being a state of synthetic individuals - but there was very little support.
So like the passive-aggressive benevolence I am, I dedicated several hundred influence+favors to force through most of the Greater Good propositions (like in a previous game), putting most of the galactic community/my federation in breach of galactic law. The sanction laws are pretty serious at this point, so this had a snowball effect of drastically dropping the diplomatic power of all those authoritarians who I (for some reason) tolerate. Shame on them! Shaaaaaame! And also now I will declare synthetic life valid, while my colony ships inch closer to the Spiritualist Empire's holy worlds.
Oh yeah, the Spiritualists awakened. That was scary for a bit, but I had enough alloy production from 3-4 ecumenopoli to construct a vast fleet of arc-emitter battleships. I'm at parity with them now, and that's not counting my 3-layer-deep line of citadels with ion cannons, platforms, and defensive auras.
... which they might just jump over with their psionic jump drives, but maybe not. I'll see once they're goaded in, and my arc-emitters *should* core a lot of their battleships anyway... and I'll win a war of attrition with my absolutely redonkulous alloy production.
This became a ramble. Yeah building large federations is tough. At a certain point you probably need to use vassalization or liberation-wars. I'm definitely going to use liberation-wars next time around, because frankly I'm sick of tolerating authoritarians in the endgame. The Greater Good GC policies hurt them, but I really hoped they'd adapt, you know?