Along these lines, Blizz already had the solution starting back in WotLK: a progressive aura that either nerfs the raid or buffs the players that stacks over time, with the option of turning it off.
The way Blizz likes to tune mythic raiding nowadays is the most inefficient and likely the most terrible way possible. Granted I still think the difficulty of mythic has gone too high in general compared to where it used to be (as is the case with most raid content), but putting that aside it's rather obvious that what Blizz is doing pisses off or annoys more players than it has to. Despite having a long career as a hardcore mythic raider (and 25H before that), I still think that the mythic raid difficulty is one of the larger mistakes that Blizz has made... and I'll admit that I was cheering for it initially. Although people felt the same way about warforging/titanforging: in its initial introduction it was actually decent, but Blizz turned it into a monster over time to where the game feels better with the system removed. If they don't scale the raids back to normal/heroic only with a dash of 'hard modes' for bosses with non-power rewards, an optional, progressive raid-wide aura over time is probably the next best idea.