It is not that farfetched of an idea. In fact, honorary spring game coaches are not uncommon amongst football programs. The Gronk brothers "coached" Arizona's spring game last year. Oregon has routinely brought back famous players to be their "coaches", and there are several other examples. 

Let Tress lead the team out of the tunnel and don the vest one more time, and then after the game, get the proper send-off that he deserves.