sadly the name "War in Heaven" just reminds me of Banks' Surface Detail, which just makes me think of a bunch of cool ideas that could be in the game, like a victory-by-sublimation for a tech victory condition
The whole 'technological ascension' victory has never struck me as very interesting from a gameplay mechanic. I've never seen a game do it well. Usually you pour a lot of money into science to unlock some device then you pour a lot of resources into building the device and you 'win'. Does that feel satisfying? It certainly didn't to me in Civ, where you fire off a space ship and hey look you won. I guess. I'm not sure WHY a distant colony with a few hundred people means you've suddenly won on earth though. I've had other games where I am dominating the map militarily and economically but someone finished a special project on the other side of the world so they 'won'.
I thought it made sense in Civilization because the idea is that you're now on more than one planet, so the scope of the game is "over" - and yeah, it felt pretty fair. I mean, you got plenty of warnings, and many of the variations had some rule like, "once the space ship is launched, you can still lose by losing your capital within X turns." Which leads us to Alpha Centauri, where the Transcendence victory was integral to the plot and did an amazing job of tying up the story themes.
As a gameplay mechanic, it works well enough. It's a game about building an empire, which you then use churn out military units that are mostly identical between equiv-tech civs. The victory typically goes to civ with the materiel advantage anyway, so why not just say, "hey, let's skip the foregone conclusion wars, and just let the most technologically and industrially advanced civ win? so long as they can get by dumping resources into a project that does nothing BUT let you win, they're already ahead anyway."
So long as the various special projects/techs/events/etc that end the game are well-written and consume sufficient resources over a long enough period of time, it'd be a good way to end the game. Instead of the insane end-game slog we have now. And if it followed Banks' sublimation model, the other players could keep playing, but the "winner's" empire would be removed/deprecated/converted to a fallen empire.