Yes, you could do this, and it may work, but the "opportunity" doesn't exist because no one else has thought of it - rather there's a hidden risk you're not seeing, which would be failing to get your USD withdrawal out. As we've seen time and time again, exchanges of any size can disappear overnight. Think of it like buying a high yield bond on Bitstamp/BTCE. If you think they'll be around for a while and won't disappear, you'll do well.
Right on, you hit the nail right on the head. Beautiful.
In terms of a creative solution, what about in addition to this arb, short BTC. If the exchanges fail BTC drops and you are secure.
Just a thought
EDIT:
Just realized that this idea wont work ^ (short btc)
REedit:
Wouldn't work bc when BTC rises you are in trouble.
BUT I realized the perfect way to do this, BTC put options! Use your arb money to buy puts on BTC and you're golden
too bad they don't exist, or do they?