PvE Arenas and would be a great idea for the PvE game as well as it relates to Arenas which already have its own PvP Arena game.
Being able to have your own 5 man team and go one and one with scaled lvl 80 Elite Dungeon Bosses from any Dungeon of WoW or of other kinds and their crew if any sounds like Fun & Win in a Arena style setting of some sort. Blizzard seems to think its a cool idea as well and could very well have some slim possibility of getting implemented in the game at some point maybe. Would be very Fun if it happened. As its not too far different from the concept of Ring of Blood concept in Nagrand and Zul'Drak but with some kind Arena style group ratings fighting lovable and despised Bosses and their crew. With Phasing technology that could be even easier to implement as well for groups in such a setting or if different settings are needed.