I like the suggestion, and the fact that you obviously did some effort to make this look good.
Point here is, in my opinion, what's in it for the gm?
Eventually the only goal the gm has is killing the group.
I haven't actually tried this sort of event, but i find myself being attacked by several non-vips pretty much daily.
I let them throw out all their anger for a little while, but after some minutes i'm bored of healing myself.
I kill them all, everyone leaves, no one's happy.
If you can think of a way to make it more retail like, as in tanks healers and dps, it might actually become a challenge for both parties.
I do like the idea.