Adding an addition to the attunement stuff that went around in vanilla and tbc which was pretty cool, could be plain phasing ... that is for newer dungeons etc. Which is released after cata release in major contet patches.
So that you had to do some quests and get some lore story around the place before you could see it less enter it. Not every raid but some of the raids would be awesome, and not make the quest chains too hard tho so the man on the street have no chance of doing em unless he got uber elite guild and friends.
I think its a pretty neat idea, along with the allready awesome phasing technology.
Also as mentioned in another thread 15 men raids is better than both 10 and 25, easy enough to put together and more fun than 10 mens...