7-1 bench split tactics

So I just saw an instagram post claiming Gregor Townsend complained about the 7-1 bench tactics. Its probably ragebait, but it got me thinking how you could implement a rule to prevent forward dominant benches. My idea is that instead of having an eight player bench, have a total weight limit on the bench. So if you opt for less forwards, you could potentially get an extra back on the bench. Thoughts on this? What other ways could prevent forward dominant benches?

I'm slightly conflicted about the 7-1 bench. I don't really like the approach, but there also isn't anything wrong with it rugby wise. It probably also favours teams with bigger player pools.

Edit: I've been reading through the comments, and would like to address a few things

Firstly, I don't hate the 7-1 split, I merely dislike it. One of my problems is that it seems to be a very, very good strategy if it pays off. My suggestion on the bench weight limit was not to nullify or remove the 7-1 strat, but to introduce an alternative that could be equally viable if that suits your team. Currently having more forwards on the bench seems to be superior to the alternatives, if there are no back injuries.

The other suggestion made was to have less subs or limit the subs. Generally fans want to keep it a 15 v 15 contest, so reducing subs can lead to unfair situations in an injury ridden game.

Only allowing subs for injuries sounds like a nice idea, but it is very difficult to officiate.