Hey, everyone. Sorry for resurrecting an old topic. I think going by the wording of the class itself is a bit misleading, as the Divine Champion PRC is sourced from the Player's Guide to Faerun sourcebook. The reason this is important is that, in the FR setting, all divine classes are required to source their power from some sort of divine entity (gods, spirits, powerful fey/demons/archons/elemental lords, whatever).
In baseline DnD, including Ravenloft, this requirement doesn't exist. Clerics can source power from intense zeal in a philosophical belief, druids source their power directly from the divine essence of nature, and paladins are granted their power directly by fate/Mount Celestia (the source for Ravenloft paladins is, of course, a bit more murky).
With this in mind, I think a more sensible interpretation is that the only type of faith which would make use of Divine Champions are organized faiths - those that have ordained, specific places of worship and the resources to sponsor an armed divine order. Given that the Divinity of Mankind is Paridon's only major religion and that it's highly organized, it seems sensible that they might maintain a few warriors who've coaxed out some divine power from the godlike nature of the human soul. However, a divine champion who follows a personal philosophical creed seems more out of a place. Likewise, divine champions coming from Ravenloft's three confirmed fake religions would be a bit odd, I think.
Just my two cents.