Mino
Similar with naktos morgue (low lvl) and USH (mid lvl), it might not be a bad idea to have another higher level thieves cave.
It will use already existing artwork but just increase their HP and maybe make them all large groups. The loot can have the infamous thief's mask. On a more regular loot level can also drop uruz/stinger/etc. The design of the cave can be a spiral (like a funnel). Sort of start at the outside perimeter and once you finish, enter door to lower level. Max I would say have 3 levels.
To give it sort of a "touch", maybe must have a thief toon open the cave (cannot be any other toon).
Also not sure if this would work but maybe, just maybe have the big boss be a criminal (so EJ works on him). Now that the drop rates of EJ have increased it would be nice to see it actually being used.
//overall I must say that everyone at RatLabs has been more than amazing and thank you for all your efforts. I wish you much success!