OK, based on feedback and some of my own deliberations, I've updated my initial post. Here are the changes, so you don't have to go find it, plus some background reasoning:
At the start of your Clean-up phase, remove tokens from here: for each token removed, you may trash a card from your hand or one you have in play.
Worshippers: changed the rule (and the mat) to "At the start of your Clean-up phase" because that seemed more clear to everyone. It felt important to keep it after the Night phase for Undercroft (which got rebranded as Cloister).
Before I show the updated cards, I will say, I am very happy with the mechanic and the general idea behind each of the cards. That said, it's hard for me to really know how valuable the difference between a Worshipper and just trashing a card is.
The benefits are:
• you can play a Copper (or other card) on the same turn that you trash it
• you can hold on to the trashing if you don't have anything current to trash
• the corollary to that is you can stock up on Worshippers as a defense to gaining Junk
• a trasher like Apse Chapel can effectively trash itself, when you're done with it
So while I can tweak things here and there, to get a real understanding requires some extensive play testing. Here's hoping my guesses are reasonable.
The updated cards:
Apse Chapel: No change. I keep going back and forth on whether this should be +2 or +3 Worshippers. While I think +3 has a better chance of locking in the "skip Chapel" vote, it feels too strong. But as I said above, this can only really be figured out with some real play testing. In lieu of that, please let me know: is +2 Worshippers enough for you to consider skipping Chapel? Or does it need +3? (and if so, what should I price it at?)
Parish: the original was just boring and really just a token Victory card (no pun intended). This new version is more interesting (and thematically better - the more Worshippers you have, the more valuable your Parishes), but it could also well be broken. If so, help me fix it! (higher cost? more worshippers per VP? or is the idea generally broken?)
Cloister (formerly Undercroft): a good point was made that it requires another trasher, so I solved it by having it trash as an Action. Thematically, Undercroft didn't seem to work anymore but I had been working separately on a Cloister, and this seemed to fit - you go to the Cloister during the day to meditate (i.e. trash cards), or clandestinely meet at night to gather future Worshippers. I considering pricing this at $3, enabling a double Cloister open, but $4 seemed more balanced.
Archbishop: Small change. I was incorrectly comparing to Bishop at $5. When I realized it was only $4, this needed to be a little stronger, in order to qualify as "Grand".
As always, feedback is very welcome. Coming up with a new mechanic and several representative cards was a big swing for me, so I hope it's OK that I'm asking / discussing a lot.