As a backup, he can't be any worse than EJ Manuel, and in fact would likely be much, much better.
If he can be had for peanuts, sign him up to a K filled with penalties for stepping out of line.
I don't see us retaining Tyrod, but if we did, and if Tyrod were to go down for a 3 game stretch (or more) Johnny Football could help mitigate the damage a lot better than other backup options.
He has definite limitations to his NFL game, but he is a football player.