I like the potion shop. You can even use the same interface for the glyph shop idea that I will continue to suggest until glyphs are in perfect balance.

Burn Salve and Fortitude Tonic do need to be ~5-8 gold, though, if you want anyone to ever buy them. Now that it's a guaranteed find rather than a lucky treat, Schadenfreude should be at least 20 gold, seeing as it is effectively 2.5 mana potions for most classes. Guaranteed Strength Potion is a nice thing for PISORFers, and will add to my amusement when I next go on a "see how high I can stack my damage at level 1" binge; even though it's usually a novelty item, 15 gold is probably still about right seeing as it is very broken in the wrong hands.
Sparkles are great for purist runs. But they don't make up for Scout Altar. Pactmaker's sparkles are nearly impossible to see in some dungeons. Between the sparkles and the bloodstains I feel like I'm playing Battleship.
More altars with more unlocks is a nice feature, although as long as you're going that route IMO you should allow a player to go all the way and get 4 altars on the map. Otherwise the limited-unlockers will just pick out six (?) deities for optimal play. As things stand, most of the deities are just too unhelpful outside of specific strategies - Mystera in particular is at her most niche right now, being great for Fireball strategies and terrible for everything else, even PISORF (literally the only cost effective boon she has for someone not relying exclusively on BURNDAYRAZ is Refreshment, which just isn't strong enough to be worth the investment in piety and sticking with her over another more helpful deity).