This is definitely one way to tackle the scourge of exchange hackers, but I'm afraid anyone clever enough to engineer these complex attack is also clever enough to cover their tracks.

Obscuring the trail of money with monero and decentralized exchanges is trivial at this point!

Secondly, I think it's within the realm of possibility that many of the biggest bitcoin exchange heists are state-sponsored, so these bounties won't do much in those cases.