I suspect Newton's people will have a pretty good idea of what he could get elsewhere.
(yeah I know, tampering is illegal and all, but let's be real)
Said it elsewhere: Asking him to play on a one-year prove it deal means he assumes all the risk. Another injury and his future earning potential is out the window.
If he knows someone else will offer better than us (like say, "ten different teams") I can't see any reason why he shouldn't pursue that.