A new kind of raiding?

Another reader post, this one proposing a solution to having always enough challenge for the hardcore raiders:

"A rift in the maelstrom has opened and an (Old God/Titan/Ancient Demon/Giant Murloc) has appeared! Adventurers are invited to take a boat from Tanaris to challenge him on his magical purple floating island.

Of course, the boss would be ridiculously hard. Upon engaging the boss, any new boats that head to the island are rerouted to a circular path around the island, preventing griefing from players not in the raid. This would create the sometime-asked-for spectator-mode for instances/arenas, while preventing the griefing that occured with Kazzak.

Actual mechanics of the fight are up to debate. I tend to lean towards any battle system that requires perfect "know your role" playing, along with a musical-chairs type event that will result in the gradual reduction of the raid, one member at a time. I would say whoever didn't get "seated" in time would be taken out of the battle, not killed but unable to help.

It doesn't really matter how hard we make the fight, though. The hardcore guilds will defeat the boss in a day or two. Upon his defeat, he will grant a buff/title/mount or some other useless but cool trinket. Maybe everyone in the raid will become an Elite? Anyway, each time the boss will also drop a crystal/vial/coin that will unlock his second difficulty available the next week.

This process of "upgrading" the boss after each defeat would create a new challenge ... ultimately upon the 8th (or whatever number you choose) incarnation of the boss he should become "unbeatable" according to Blizzard. This is the key to this challenge. I believe Everquest did this with some dragon or something, they didn't intend for the boss to be killable, but it was.

Here's the second key part. The boss should be tuned in a way that he is only defeatable at his easiest difficulty if everyone in the raid is in full Tier-whatever. This way, when guilds beat their chests and proclaim that they've defeated the 3rd-Crystal Giant Murloc (or whatever he ends up being) the rest of the world knows it is due to skill, not gear.

This boss would have no trash to clear, and would be relatively simple to implement. It would provide a severe difficulty curve at the very apex of raiding ... a challenge that would keep the most hardcore guilds busy with a goal, but wouldn't provide a massive time-sink on the part of Blizzard.

So, what do you think about it? A boss with several difficulty levels, from very hard to unbeatable, giving out highly visible status symbols as loot, not gear. Does WoW need an ultimate challenge?