You COULD lower the humbucker height, though this will effect the dynamics and stuff. If you added a resistor to the humbucker to "turn it down" a little, it'd lose a lot of top end. I suppose you could get round this by adding a resistor and a cap (to bleed the treble through) to the humbucker, though I'll have to look into it for you.
Calum
EDIT: I was talking to a friend, and apparently the resistor/capacitor idea would work, but the pickups would sound like cr@p. Can't you just turn it down on the bridge pickup or add a compressor or something into the guitar? I really do think it's more effort than what you're gonna get out of it.