I think most people agree that rugby teams are too heavy. Players are under too much pressure to bulk up, beyond what is healthy. Bigger pack weight does give a big advantage in a match, but it does not make rugby a better game.
There should be a maximum team weight. Maybe 1500kg for 15 players. Teams can still use very heavy players, but they must keep the total team weight under a limit. So being very heavy is a slight disadvantage for a player. The existing incentive will be reversed, to keep below a limit, to a healthier weight.
Very heavy players will still be selected, only if they are skillful enough to be worth keeping, despite the difficulty they create in keeping the team under the limit.
This does reduce the advantage very heavy peoples like the Europeans have over lighter peoples like the Asians. So it might be unpopular among supporters. I think it would instead make things more interesting. It would mean more teams can seriously compete in international events.
This is just asking for weight cutting like in fighting and wrestling. I'm not so sure weight cutting is any healthier than the weight issues you're describing.
Yes I'm sure that would happen. Good point. Only the heaviest players would feel the incentive to cut weight. But this would only affect players over 100kg, already over the average weight for a rugby player. So if the few heaviest players feel a pressure to cut weight, that might not be such a bad thing.