All level 50 dungeons should have 3 boxes to choose from in Df, low level, high level, and expert.

If you pick low level, it should be il 50-70 and sync you beyond that. It should reward the lower type of tomes, drop crafting materials from the mobs for il70 equipment, and have il70 gear in the chests. Newer 50s would run this version to gear up for LAB, HM primals, and gain tomes for il90 gear.

If you pick high level, it should be il 70-90 and sync you above 90. You should get a decent amount of the lower level tome, and a small amount of the higher level tome type. mobs should drop il90 crafting materials (rarely), and have il90 gear in the chests. You would run this dungeon to gear up for ex primals, second coil, and CT.

If you pick extreme, it should be il100-120, it should give a large amount of the lower level tomes, a decent amount of the higher level tome, il110 crafting mats from mobs, il110 gear in the chests.

Once we get capped at il60 those dungeons should have a similar format. But all level 50 dungeons should easily be scalable in this way by simply increasing HP, damage output, and damage resistance on the trash and bosses. Add a few extra abilities to the extreme versions and you are all good. Everyone gets to try all the content at their own level and get some rewards.