Yes, Survival/Horde mode.
Gear changes allowed every few waves, but waves have varying elemental affinities.
I.E. You can get fire based wolvers alongside ice based kats and shock based chromalisks.
Done right, could be interesting.
Leaderboards are the #1 replay value.
Ydub.
I made it already. Well, something like it.
http://forums.spiralknights.com/en/node/49662
Besides, OOO has yet to release those' Danger Missions' they promised a while back.