I reworked the cards, but I'll get the mock-ups up later. For now, text.
Confession:
+2 Card; +1 Action; You may trash a Curse. If not, discard a card. | In games using this, when you buy a Duchy, you may gain a Confession (This card is not in the Supply.)
I don't think it's stronger than Warehouse, strictly speaking. Warehouse is choose the best 4 cards out of 7; Confession is choose the best 5 out of 6. But it's also harder to get than Warehouse, since you can only get it by buying a Duchy. (I recognize the version originally posted had it gainable with any Victory. It was originally imagined with Duchy or Duchy and Province.) I've moved the curse-trashing ability to this instead of Sinner, since it makes more sense thematically and now fits in with sinner's new exchange conditions.
Sinner:
-2 VP; +2 Cards When you discard this from play, reveal your hand. If you have a Confession...
in play, you may exchange this for a Novice
in hand, you may exchange this for a Heretic
The conditions for moving into one line vs. the other are now different, but both dependent on the same card. The curse trashing moved to Confession, and the different conditions does not now oppose Heretic line's self-cursing.
Novice
Two options. 1) keep it more or less as is, but revert it to a regular action (not Reserve) and change the exchange conditions to "While this is in play, if you buy a Province, you may exchange this..."; 2) change it to a regular action that reveals cards until revealing two actions; choose one of them to play it. Still on the fence about which.
Heretic
Essentially just changed it so that it only stays out to the next turn. But I might need to add some sifting ability in that draw (set aside Curses or Victories?) to make it a bit stronger. That or extend the draw-up-to ability to the turn you play it as well as turn two. Exchange condition still dependent on buying a Province
Nun
+1 Action; 3 Cards; You may trash a card from your hand; You may trash a Victory card from your hand and gain +VP equal to 2 less than its cost in $.
This roughly puts the VP gain equal to its face value for many VP cards, some more, some less.
Arch-Heretic
Still working on this. I'd like to keep the Curse = 1VP, but the wording is entirely too long and doesn't leave me much space on top to do what I want. Another idea I'm toying with for it is:
+$3
Put this on your Tavern mat. Each other player reveals a Confession from their hand. If not, they gain an Excommunication (essentially an untrashable Curse). | While this is on your Tavern mat, when another player trashes a Curse or Hex, they put it in their discard instead. [Or alternately, ...Curses and Hexes cannot be trashed.] | When you buy a Victory card, discard this from your Tavern mat.
But as it stands, there's too much text. I need a simpler way to accomplish this. Or part of it.