I am assuming this idea came from the fact that pvp gear raises/lowers in pvp/open world content. I disagree with this method.
Imagine a raider or M+ player 250+ gear getting lowered to 220 in open world content. I suspect there would be riots.
If something like this would be implemented, it would split players into only doing that content and nothing else. (This happens already, lots of people only doing raiding/M+/pvp/open world content.) But it would make that division even deeper.
It’s bad enough that bliz tempts player and/or forces players into that content already. Example: The covenant story takes you deep into the maw, torghast, etc. The story puts you in dungeons and raids. This week is mythic dungeon week with the loot temptation.