Oh, wow, I spotted this far later than I would have liked, as there appears to be a growing crowd. That said, I would definitely be interested. The world needs more evil. That, and I always wanted to try out the cloistered cleric, and divination/abjuration mesh well with a certain level of metagaming.
As for the corruption itself, I wouldn't be as certain about building up fronts, since after all the point of having a corrupt champion is to then let them be turned on a genuinely good organisation. Infiltrate and/or frame the organisation, sure, or have affiliated fronts to feed things like prophecies, but in the end the Holy Order of Artemiana needs to be taking the fall, and I assume they generally aren't bad people on the whole.
I also think that star-crossed lovers and the like are always a reliable way to go, as they tend to, or at least are able to, emphasise the ways in which it's the personal character flaws that ultimately lead to the downfall. Especially if the flaws aren't really flaws, per se. Someone's personal loyalty to their friends is usually quite admirable, but can drive you down a dark path if you see those friends betrayed or persecuted by an organisation, all the while blinding you to the fact that the organisation might have a point, and your friends really were corrupted or puppeted by some mysterious conspiracy. It also makes it much harder to atone when your ultimate fall is a whole-hearted spree of vengeance rather than a manipulated gotcha moment. You can feel bad after you realise you've been tricked into doing something you didn't realise was evil, but it's much harder when you think you really do have a point and they had it coming. And even if you do realise you were tricked, the betrayals become much more personal when you realise it was your close friends or lovers, rather than a prophecy and destiny.
Prophecy and destiny should of course also be involved, but I tend to think that it always should be intertwined with and contrasted against the personal. For one, it makes the people inflicting this sort of personal emotional trauma a far nastier bunch. It's one thing to weave fate so that someone falls. It's quite another to murder their best friend then use the corpse to trip them up. *twirls mustache*