The problem is that in that scenario, it's not a fair contest for the fullback. Fullbacks are on a hiding to nothing as they are generally stationary under high balls and get belted by fast moving defence. Classic case of one player playing the ball and 13 playing the man.
I actually think there should be a rule change to reduce risk of injuries - a player should have the option of calling “mark” for a catch inside his own 20m area and receive a play the ball (tackle 1).
I agree with the first part of your post- fullbacks are just sitting ducks under the high ball with no protection. Bombs are a massive blight on our game in any case- they are a crap tactic.
As for changing the rules to allow for a "fair catch" NFL-style I don't agree with that- that sort of thing is just Americanised rubbish along with "taking a knee" to kill the last few minutes of a game, would hate to see RL reduced to that.
**The easiest solution is for the NRL to actually have some balls and heavily suspend players who make contact with the head of a player (especially a defenceless one like a fullback sitting under a bomb). They are the rules of the bloody game- no contact to the head.**
Kade Snowden broke Ray Thompson's jaw in an incident that was more innocuous and less ill-intended a few seasons ago and got 8 weeks from memory. As the NRL have proven regularly, punishment depends on who the person at fault plays for and the vested interest the NRL has in that particular player's team being successful. The tribunal has just been an absolute dog's breakfast for many years with punishments taking on the form of a lottery. The NRL having no balls is the root cause of all this crap. Corrupt as you can get.
Would be interesting to see what would happen if Jazza "this is my house" Hayne gets his jaw busted on that annoying looking head of his this weekend and the NRL loses it's golden meal ticket for the rest of the season, punishment would be more severe you can be certain of it.