With single platoon, limited substitution football, players would have to go both ways, so they'd have to have a wider range of skills. With limited substitution, there also wouldn't be position specialists like punters and placekickers; they would be replaced by real football players. It would be a better game, especially if we also widened the field to rebalance offenses and bring the run back into the game.
And while I’m at it … big time football needs to tell the television networks that they’re taking the game back. No tv timeouts to disrupt the flow of play. Speed up the game. Once again, the NFL fatties would have to downsize if they couldn’t count on long rest breaks every few minutes.