What's an "expy Christian church"?I honestly found Ezra (from DoD) one of the best additions to Ravenloft as a expy Christian church that is very needed in gothic storytelling. The old cathedrals, exorcists, inquisitions, etc. When domains were flyover country that your primary goal was to not outstay your welcome, it didn't matter what god the local church was, but once you get local PCs, it mattered.
On a side note: I like Hala as well (coming from the 3e era) as a kinda expy Wicca/pagan goddess worship option. Those two fill 90% of the "good" religion needs of the setting and still keep enough mystery to not be completely wholesome. For me, it was nice to have a faith or two you could get holy water from.
Eberron csn also add the cost (heavy almost but very much not catholic church structure type vibes), a couple with links to more eastern style Buddhist type fairs (path of light & BoV) , and even a "mesh whatever, I go to church because I guess I care" conglomeration of faith in the more generic sovereign host.after doing write ups for each eberron faith I bet rthe wotc folks can give at least one or two thematic and obviously inspired by but ridiculously wrong for the good of plot type faiths in the ravenloft book