For running lower level content (specifically including normal world questing and stuff, not just instanced stuff like dungeons or raids), I think it would be really useful and fun to be allowed to opt-in to temporarily lower your level to that content, with a comparable reduction in stats to your gear/iLVL. This could be similar to the Party Sync feature, but for solo players who want to experience zones and stories without having to xp-lock themselves into Chromie Time. There is already a system of scaling-up stats on most gear in leveling zones while in Chromie time, so I know that the systems can do this in an effective way, just in reverse in some cases, and temporarily.
I have just finished running all of Eastern Kingdoms and Kalimdor on my main, and have decided to undo the XP-Lock so I can go to the Dragon Isles for a while before going do more old content. I had played during Burning Crusade and Wrath, but I haven’t been able to experience the vast majority of WoW content, and I really would love to be able to experience it and the stories therein, but without accidentally instantly murdering every boss monster with my weakest possible spells/abilities.
There might even be a system of reducing your class points, so you have to work with whatever class and spec points you can use at those levels. Potentially there could be “level sync’d builds” saved, too, that could be switched between in a similar way to how builds are switched between now. However, this might be too difficult to implement honestly, and I think the level/ilvl reduction sync would be enough.
I know this has been on-and-off requested repeatedly throughout the history of WoW’s expansions, but with the new sort of design ethos I’m seeing with Dragonflight and The War Within, and a lot of features I had been so, so hoping would show up or return suddenly appearing in the game, I’m hoping that some of these other long-requested features might actually start showing up.