A generic Path base class? So a class where every level or 2 you get another step that can be chosen from several Paths. This sounds almost exactly like the d20 Modern and Spycraft 2.0 Back to Basics classes so maybe you can start to look there for ideas.
I know the Paths ramp up the power level at higher ratings so if you went with a Path progression higher than every other level (which is where the priest currently sits), I'd be inclined to cap the Maximum Path rank by class level.
Setting the maximum Step at levels 3, 5, 7, and 9 for II, III, IV and V respectively would keep it in line with the existing power structure.