I wouldn't mind bringing back class regents, class quests, class skill training and removing guild perks. Everyone could have a reagent pouch such as the key ring, with all class ingridients there (and hunter ammo). Then let everyone have some sort of teleportation item or spell (just like Druid Moonglade teleport or DK teleport), to bring them over to an isolated class area where they can level their skills, buy their reagents and progress their class quests.
I also think that it's a shame that elite mobs, instance patrols and un-instanced mobs around an instance area were removed. The journey into finding the instance portal was a quite nice feature in Vanilla I enjoyed. Not having elite mobs and hard quests baffles me, and I never really understood the point in removing elite mobs? The whole point of having those kind of quests was to delay doing them until you could get help from friends or randoms, which I undoubtedly see as a good thing.
I know this is a 'for fun thread', but may as well discuss the subjects presented.