I don't know if you know this, but a coach is more than just a playcaller. Coaches teach, come up with a gameplan, come up with plays, schemes, and everything else. Just because he ran the no huddle doesn't suggest a good coach. Kelly has said over and over that he does NOT want to coach. Can that change? sure. But he feels VERY strongly about it. This isn't something that he just slips when he is asked, he brings it up first that it isn't going to happen.
And yes, this was a hypothetical question, but it doesn't spark any good conversation. Kelly has been out of the game for over a decade (the game has changed a lot), he has no experience, and he doesn't even want it. No one is going to like the idea unless he comes back as a Quarterbacks coach. There are just so many better questions to ask.