So, having had time to sleep...
Phyrexian Unlife!Format: Effectively the same as just starting with 30 life. There are some quirks (like how you can run some creatures with Infect without having an explicit "infect deck"), but most of the weirdness basically requires one player to be losing quite hard to matter.
Transcendence!Format: You go from 0 to 20 instead of 20 to 0, with the added quirk that lifegain basically doesn't exist. It'd play mostly like normal Magic (since lifegain is kind of an incidental thing
anyway), except card evaluation would get flipped over onto its rear. In all honesty, the card pool to make this interesting probably isn't there, but eh, that's why some ideas stay ideas.
Worship!Format: You're right that it would make life loss (and removal) more important than it traditionally is... but I'm worried about the old
Form of the Squirrel problem (where you'd teach someone new the importance of playing removal by playing Form of the Squirrel and keeping the squirrel out of combat). You could probably make something interesting out of it if you focused
really hard on encouraging blocking and combat trades, but then the question becomes "why aren't you just doing that as part of a normal cube?"
Crumbling Sanctuary!Format: Seems interesting. Three things come to mind:
1) It'd be pretty easy to exclude cards that make your opponent lose life, which would mean that you'd effectively start with 19 "life counters" that you can spend on stuff. I'm not sure that there's enough "pay life" stuff to make this worth it, but it's interesting.
2) I would tweak the wording of the "exile cards" effect so that it works with cards like
Crosstown Courier... because making Blue the format's Red is
hilarious to me.
3) Having a tension between "damage mill" (which exiles) and "normal mill" (which doesn't) seems like it might lead to some nuanced game states. The ideal would be to have
Book Burning present a hard decision, even though it's literally just a choice between "mill 6" and "mill 6".
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As a general rule, I'm not super excited by "card emblems" that
solely fiddle with the win condition (the Capitalism Cube is an exception in my mind, since it
also gives you a Treasure when one of villain's things dies, which changes the overall value of creatures and removal over the course of the
entire game... and I'm still not entirely happy with the cube). Unlife and Worship both only matter when the game is about to end, which is only a fraction of the game.
In general, when I look for a card to idly consider building a format around, I look for stuff that will come up at least once a turn if play is progressing "normally" (or stuff that's just plain
wacky). You get way more mileage out of, say,
Fae Offering!Format or
Slagstone Refinery!Format than you do out of
Near-Death Experience!Format, after all.