I think that if I were to do a 6e, I'd bring that back. I'd really try to figure out what each tier of play was supposed to be for and try to bake that into character progression.
Heck, now that I think about it, I could see having an option for the game to "stop" at that level while still allowing for some sort of progression. As in, if you want the PCs to just be "dungeon-delver" types where fighting a dragon is and always will be a Really Big Deal, then after level, say, 7-9, you don't go up in level anymore. If you want to go into a domain management type of game, then you could progress to level 13-15, then stop. If you want to become a godling, then you can go up to level 20 and higher.
Or something. I'm obviously blue-skying here. It would take a lot of thought to figure this out, and I'm not practiced in game system design.