Well, I modded my game enough to want to play it, I've got some cool snakeman slaves, and now I have a persistent crash at a specific time. Back to waiting for the game to get good, I guess.
I believe the only way you could do it would be to give a player pursuing it a very different set of rules, or a strong chance for all sorts of disasters/end game events occurring from pursuing it.
That actually sounds a lot like the quest victory in Fallen Enchantress. For more complicated stuff, I like that Galactic Civilizations (at least 2, I haven't extensively played 3) actually had ascension function in a sort of "king of the hill" manner: You seized and controlled specific points and built bases around them to harvest their divinity (or something). It didn't make a lot of conceptual sense, but the gameplay mechanic worked fine. Now, in Stellaris this could actually work better, because divinity and religion and psionics all go together, and there's also a trait system. So you could get a holy special resource somewhere, and not only would it be a ticker to victory (as in GalCiv2) but it might lead to new psionic traits for your pops or empire, making ascension something that's valuable even if not pursued all the way to its conclusion. There could even be a balance: Spend the ascension resource to make your pops godly, using an addition to the UI for genetic modification, or save it all up for when you unlock ascension, and bring your whole empire beyond the need for physical form all at once.
yeah. I've been trying to come up with some way to make a science victory condition interesting from a mechanical perspective.
All good ideas - I feel that scientific victories could actually be made very interesting just by making it an almost 50/50 chance of going disastrously wrong. It'd be a bit of a gamble (or desperation move in some cases) and you'd definitely need to risk tackling particular AI players who decided to pursue it.
That, plus factional outbreaks and you'd have a pretty good end game condition!
Regarding AI, they could take only the non-slave pops from their founding race (or races eligible for leadership positions, to support more egalitarian empires) and the others get left behind. Then just set some events to make the remnants of the empire collapse into warring factions (new empires, each one at war with each other and with custom war goals as necessary) and you've got a major political event that keeps the game interesting and fun.