It might be interesting to give the Priest one or more deity-related abilities, since oddly the Church lacks those generally. (Paladin's monotheism, and that's it. If we count the Crusader as an honorary Church member then we also get the extra altar, but if we do that then I get to complain about how the Fighter's Guild needs a fourth tier member.
)
What if the Priest got Scout: Altar? Not the really powerful one that was formerly a prep, just show the one tile for each altar in the dungeon. Maybe a built in Agnostic Collar? Call it "Sanctification" and let him desecrate rival altars for free. That'd get the indulgences and piety covered. Both would also maybe be useful teaching tools for the power of deities / the power of desecrating.
(I actually don't think the Priest has a significant problem worshiping GG. Now, yes, the
Halfling Priest has a tough time, but that's more because Halflings, like Gnomes and Goblins, don't get along too well with the old man. Those of us who aren't obsessed with the various "drink a ridiculous number of potions" strategies
make do just fine by keeping a careful eye on available piety and altars to convert into or desecrate.)