To get anywhere near a decent picture of the network you're going to be asking a lot of peers for proofs at significant processing cost, and I'm not even sure if it's in their interests to supply them to you.
If you're honest and you're really storing the blockchain, it takes less resources (CPU/bandwidth) to compute a response to the proof-of-unique-copy challenge-response protocol than to send 10 random blocks asked via "getblocks". So providing this protocol does not increase the DoS risk.
Anyway, it's just an new idea. It's not something to rush to add to Bitcoin.