How about instituting the power play, if a player commits a penalty, they sit out a play and the other team has a man advantage.
Or do like in Soccer, and if a player commits two personal fouls in a game the team is shorthanded the rest of the game.
I would like see two points to the defense for a turnover.
That might take some of the emphasis off the passing game and we could get back to old days of three yards and a cloud of dust.