He could still be hit hard with a legal wrap up tackle. The better way to treat this is for the pop-up kick to be the same as a pooch kick that never hit the ground. The return team could still signal for a fair catch. They would be protected from being hit until the ball is caught just like any other kick. If the kicking team catches it in flight, it would be KCI. It saves time from having to stop the game for penalty enforcement and lining up for a new kick.