How about exclude casters (clerics, wizards, sorcs, {bards?}) from being able to take CE and do away with the toggle? I doubt it would overpower rangers and pallys. Casters would have to multiclass in melee in order to use it (a very big trade off). Perhaps add a smaller AC bonus, which also does not toggle off, to the combat casting feat. It might make this feat a little more useful to a caster. edit - okay, not such a good idea for pallys & rangers to have access to this unless it too had a to-hit penalty.