I really thought savage coil was great for this type of thing. A reason to max out your gear and a nasty challenge for those elite who find coil to easy. Shouldn't require a lot of extra dev time since most of the assets are reused, only should need a token reward because the reward is the challenge itself.

It just needs to be implemented in a way that doesn't interfere with current coil farming. (biggest drawback of savage scob).