Appreciate the idea however personally not something I would entertain.
1. We did rebirth on Project69 - no one chose to lose levels! It was rather unpopular
2. The cap is really there to slow everyone down and prevent power getting out of control, this is rather contrary to that
3. As above it would probably be more elegant to just add more levels to soft cap and ramp up the difficulty to level (essentially how it used to be!)
I do agree something more tangible needs to be given to those who are a high level. Heroes League buffs are really effective but I don't think anyone really has a sense of that because it is just not measurable (outside of us reviewing logs!). This means those at high level don't really feel any achievements and those below Heroes League have no desire to achieve it.
I have an idea for you, for higher lvl people.
How about, when people reach lvl 185, they can become a master (with a dojo) take on disciples? Kind of like a sub-guild, but more like marriage. Dojo's can have a master and 10 student
* If people hunt with their masters, or as school, then they get an XP (and maybe other) bonus.
* masters can challenge other masters in 1v1 or dojo vs dojo.
* Dojo league. A league table for people who have the balls to go into dojo's and challenge masters to 1v1 duels.
* Dojo's can have their own quests so they can unlock the ability to spawn training mob/ bosses, or add features to the dojo's. These mobs dont need any drops or anything (but could haha), they would only be accessible there so masters and disciples can practice killing them.
*Every master could have one of the random buildings in the game to use as their dojo - If we run out of buildings we could always have a few small maps with buildings for this purpose (although, there are that many buildings in-game, and that many unused areas that i dont think they would be needed. They could easily be upstairs or entered from behind buildings, so no visible entrance is needed).
Just thinking out loud now, so ill stop. It would be a cool addition and add more playability and something to work towards into the game.
(Guilds could have multiple masters and be made up of multiple schools, kinda like how real guilds work re businesses coming together to form guilds).