well, i don't think forcing the player to put off all headgear is that good.
our solution atm is a modified lod-gap-solution or whatever one should call it. the gap is still 0.05 but only the inner textures at the front of the helmets were removed in the lowest lod.
first responses from our testers sound encouraging, as you have to crouch on the ground close to the model and look upward to see the difference.
and to be honest i'd prefer this lod-based solution rather than a scripted one which yet could cause probs in multiplayer.