In competition things like that would be better solved with some sort of honor code. Unless the teams and cyclists themselves enforce that GC riders stay back there will always be an incentive to try an be at the front because you might get shafted if others do it and you don't. In essence it has to be seen as not done by the cyclists themselves and its difficult to build up such a culture. Think this was more of a thing in previous eras were the peloton had more implicit rules and leaders.
But as said, a hard rule could very well be deemed to undermine integrity and/or cyclists would still be incentivized to get the most out of what the new rule still allows.
Perhaps, if Evenepoel turns out to be a fantastic GC rider, we might see teams like QS contribute to such a culture but then again they might become a new Sky as well.