Super Questing is simple it's Super Questing.
Once you have reached max level with two characters, you unlock the ability to Super Quest.
Super Questing is for veteran players that Phase onto another dimension. This Phase allows access to an Isle that is exactly like Timeless. Except THIS ISLE is for people with 3 possibly 4 Heirlooms or more. Mobs gain a tremendous amount of power, but grant mega Exp. There are 3 scaling Isles, to allow highers levels to spread out more.
You tie in the Super Questing Zone with tie in lore. Possibly to bridge an explanation of the past, much like Tier 5 and Caverns. Or an Epic battle? Whatever Blizzard wants. Also, you can do these quests until an arbitrary limiter is set.
Would it smash current questing? Is this something that should happen for Heirloomers?
Check this out, but remember 2 max levels rule. Which means if an expansion happens, you lose your ability to Super Quest and must get another 2 max levels.
I think this solves a lot of issues I have with leveling and something I thought might be interesting to others. Probably wrong.