Marauders are the only thing tied to the midgame year right now I think. Both the Khan and when they start to offer themselves up as mercenaries. I think. Never used them for that so I barely pay attention to the notification.
Anyway, I gave the voidborne start a spin and it's really cool. Definitely changes the feel of the game in a measurable way for me. You start out very powerful, but it's really hard to expand early on. The ability to build science districts without using up building slots really helps with early science, and unless I'm crazy you also start out producing more unity than normal. Traditions seemed to come much faster.
I suspect the real pain comes about 2250 where you're struggling to keep up with the expansion of other empires. About 25 years in and I've only scraped up about half of the alloys needed for another habitat. That said, you don't spend as much time waiting for a habitat to be useful as you do a planet, so maybe it balances out. Another issue I'm expecting to see is that building slots are at a premium still. I tend to build with a gene clinic on every planet for the amenities and RP aspect, and that's a building slot I really want to recoup for habitats because getting even 40 pops on one is a bit tough without exceeding housing.