Funnily enough, I have a rough plot for a forum game where the combat is simple roleplayed through. I'll petty much be there to only say if X will work and to smite god modders and mary sues, plus setting up the challenges. It got six characters slots(labeled Vamp(the hero), Ghoul(Big guy), Were(The lancer), Demon(The smart guy), Angel(the 'chick') and human(the six ranger).
Hell, with no mechanical, I could probable run it at the same time as this without problems once I have a idea of the ending.
I actually have seen two games like this and I played them both, let me tell you, they're fun. Do tell if you decide to do this.