Seriously, one of the "problems" with asking for this is that IF we were givien the "leave the pitcher in if he's throwing a no-hitter" option, then somebody else will want an option for "leave the pitcher in if he's throwing a shutout", or ""leave the hitter in if he has a shot at the cycle". Where does it stop?
In the context of the game, no-hitters are a statistical anomoly. You don't get an extra bonus in the win column if you get one. While they may be "fun", they provide nothing more than trivial value to a 162 game season. The downside of allowing SIMMY to override pre-set pitch counts, i.e risk of injury or excessive fatigue leading into the next scheduled start for that pitcher, far outweigh the benefits, i.e. meaningless trivia.