This argument is cyclical, too cyclic. Periodically someone open a thread asking if mining power can be used for projects like Folding or SETI (and only these 2 projects, NEVER other projects, never)
As always the answer is no.
You seem very sure. As mentioned above, while Primecoin does not give ground-breaking results, it's still different than Bitcoin(apart from re-used source code). So yeah, you have no proof that it can't be done.