The most applicable custom content would be a green server with different item drop locations and NPC stats, for every timeline refresh (along with other various quality of life improvements and alterations to fill out the classic game world), so that people get to actually play Everquest again. It's only Everquest if people have to explore and discover and experiment, rather than everything already being known via wiki. Take me to the Norrath where Runnyeye, Everfrost, Dalnir, Nurga, Temple of Frozen Shadow, etc have groups constantly going there, where the whole game world feels alive and there is far less crowding around a handful of zones and NPC's.
I don't think it would be difficult to gather a group of thoughtful volunteers to create that kind of environment either. This group of developers would just be moving/adjusting already-existing things within the game to make it a better experience for the players, to bring back the classic Everquest adventure and local color. If time allows, I would be all for further cosmetic alterations as well, that remain entirely in the spirit of Norrath, like undead Ogres or whatnot in specific zones, as this post shows is very possible -
https://www.project1999.com/forums/s...33&postcount=9