If this were done, you'd have to limit it to only miners of a certain size seeing as miner with my hashing power, a mere 85 gh/s, would probably have difficulty solving a current block in a reasonable amount of time to prove my software/hardware was working correctly.  Yes, I understand I might get lucky and solve block, but that would definitely be a something that could reasonably be predicted as to when.  Right now I'm showing a best share as 12.8M.  The other thing this would beg to question, is wouldn't this hash power be put to better work hashing on good work.  Seems like looking for statistical anomalies and watching them more closely, or auditing their work would be a better way to handle this.