"I'd go to a shop that knows what it's doing/has a bit more experience. Anyone suggesting drilling a hole in that would get laughed at round here."
Amen. I wouldn't let anyone suggesting such a bodge anywhere near my bike. Aside for the warranty and potential safety issue, if he's not intelligent enough to be working out a better solution, should he really be working on people's bikes? 
It's your call, but I say name the shop, so that others can avoid it.