I feel you! It took me more than a week to decide what character I wanted to play for this RP...and then I changed my mind a couple of times while writing the CS itself :lol 

I was actually planning on rolling a "fallen" paladin of sorts, but decided to go with a cleric instead. I can definitely see it working, plus you have the paladin Oaths which give it a nice flavour and can be tailored to work with any alignment. Oath of Vengeance is a cool one for example, it emphasises victory at any cost over your enemies and while it's normally sworn against evil beings, I don't see why a champion of a darker deity can't use it.