I think the best thing a citizen can do at this point is to demand of our homeowners' insurers that they not cover certain breeds of dogs--that will identify the remaining pits as pets of the improvident and thus a danger.
And our local shelters should not attempt to place any pits in homes--just euthenize them immedicately.
Some insurers already have put your excellent idea into practice (look at the fine-print "Adendums" to your own policy -- you might be surprised...