I think everyone (players / players union) in the NFL is scared how this could play out.
If a player wants to redo his contract and the team has no qualm with it, not certain why a player can't give any money back. I'm not a contract attorney, but if both parties agree to redo the contract, not certain why that would be illegal.
I could see Wentz writing a check if he is a true competitor and want to see what he's capable of. The reality is Wentz is already a millionaire and has more money than he knows what to do with. Added the fact, that the guy really does seem like a nice grounded guy in real life. I think Wentz wants to play for Reich again, and because Reich is no stranger to the eagles, and if there ever was a situation for a "back room deal" to be made, it's Wentz to Indy.