Hmm, interesting idea, but I would probably approach it from the other side... that is, keep the existing Normal and Savage modes with their current differences (enough players already have trouble with the mechanics of Normal), but introduce Echo mode (i.e. 'Hard mode') much sooner. The catch would be though, that at this stage Echo mode would only drop Normal mode loot (with maybe a few extra tomes) and once you enter a Raid (or Trial) in Echo mode, you are locked out of Savage mode for the day / week...

The idea of this would be that Echo mode provides a sort of training mode to Savage, allowing less skilled groups and new players interested in Savage raiding a way to learn, or at least see, the mechanics without smashing their head against a wall for weeks on end (or waiting for it to be become nerfed and irrelevant).

As far as providing extra challenges for the truly skilled, less telegraph markers would be a good one, as would min iLvl challenges, and not sure how easily it would be to implement, but they could also have the boss mix up the mechanics... i.e. instead of always doing A > B > C > D, they could do B > A > D > D > C (or even random orders in some cases).