I think I'm going to try life seeded with either mechanist or barbaric despoilers. Seems like an easy way to get around the main problem of lifeseeded.
It doesn't allow mechanist for some reason (not sure why). It doesn't take that long to get robots, though - the time saved isn't worth the loss of a civic anyway IMHO. You still have to get droids before you can colonize.
Starting on a 25 tile Gaia world is only really useful if you're planning on building tall. If you're going to rush right out and raid neighbors and take their people and colonize all the worlds, it's probably not worth the civic. The huge science production of a 25 tile Gaia homeworld without needing additional systems and planets can really get your tall game going, though.
IMO they need to move these two new civics (life seeded and post apocalyptic) to the "Starting Solar System" tab. Or have a new start section. Neither of those are really worth a civic - civics that could be getting you 10% more minerals or 15% unity or 15% naval capacity or -20% edict cost. It's a fun start and makes things quite different (and life seeded is good for crazy tall builds). Or if they were making a starting conditions tab, Syncretic Evolution and Mechanist could go there too and I'm sure they could come up with a lot of different starting states. Start as marauders, or nomads, or a lost colony, etc.
BTW, you can't gene mod the Gaia preference away - even with evolutionary mastery. So not only do you permanently lose a civic, but your main pop permanently gets -100% habitability for everything other than Gaia worlds, ringworlds, and habitats. A big trade off for starting on a 25 tile world.