Your suggestion is quite an old one
I doubt anybody has ever suggested it as a challenge option.
it needs a lot of work for a limited use
A lot of work yes. But limited use no, because every time you watch a game, you would want to coach it by yourself. There would be tons of games like that. If you had friends in the game who want to play those games as well, you could arrenge pick-up games at a suitable time just for the reason to coach it yourself.