The fact that Williams turned down what to me appears to be a sweetheart deal to get his life straightened out tells me that there's no way he'd be worth the risk. It's true that you're almost never going to be able to find a roster of perfect angels to put on the field but you at least want your devils to be effective and reliable. You pick your moments to add players who are "free spirits" and try to avoid the outright cancers as much as you can.
Ricky Williams is not a good risk. Nobody could convince me that he's ready to focus completely on playing football after he turned this down. I believe that the only explanation possible for him to refuse this overly fair arrangement is he has no desire to play football again or at the very least he hasn't enough desire to do it for a team to rely on him.
Fitz makes bad decisions. That's not going to change.