I think one of the problems is;  there's no guarantee about which order the miner tries the nonce values in, and it might fail or decide not to try some subset of nonces of the winning one is one of... without being a "cheating" or withholding miner.

The other thing is sending miners some fake work units:  results in hashing power being wasted,  so great care must be taken for the "fix"  to  not have greater  expected total losses on average,  than the block withholding attacks that are likely.