While I am in support of his come back and hope he makes it. I also would like to think if he is to make it, it's with the intention of more than what you said. Not to the extent of playing regular 90 mins or week in week out but you simply can't afford to have a player starting a game, expecting to only last the first half and likewise while in theory it is good, you can't have someone on the bench who is there just for a cool head in the dying moments of the game, it's a waste.
At the very least having him around is going to be a great inspiration. I hope he makes it but I also hope there is some middle ground between playing every week and the role you've suggested.
It's not the end of the world if he gets a contract but doesn't end up playing much, sometimes things don't quite work out and he will still bring something to the club.