Lots of great ideas.
I especially like the idea of having the encounter "scale" to the levels of the party who is entering it. That would be an instantaneous content increase of like 100% since you could go back and replay all the quests from any level, and have a good time of it. A really great idea.
Regardless, I still think treating elite as truly elite, with an appropriate loot bonus, would help some of the issues we see. A level 14 casual player with casual gear is truly 6 or more levels different in effectiveness from a well equipped player, and probably 8 levels from a hardcore grinder with all the raid loot.
Just my 2 cents.. Thanks for keeping things civil.