You know what would be cool? Borkedcoin where every instance of sha256 in bitcoin protocol is replaced by md5 (Merkle tree and pow), so we can see what happens when sha256 gets broken, all for science ofc.
This is overhead, just replacing GetHash() of CBlock should be enough.
Also, md5 isn't so easy to crack to do it on any PC, is it?
Good idea, anyway.