Bombs aren't that hard to stop. You get a winger who can catch and you get the centre/fullback, backrowers etc to shield him. I've noticed this being done a few times this year, especially when teams are up against Folau.
Bombing is a legitimate tactic, shielding is a legitimate defence against it.
So don't ban it, don't limit it. And whoever suggested the automatic 20m restart for defusing a bomb - there is one problem with your suggestion. This eliminates cross-field kicks to wingers, chip-n-chase kicks and virtually every attacking kick that isn't a grubber.
If 5 one-out runs and a bomb to end the set are a team's only attacking option, the fault lies with the coach and players, not the rulebook.