Mean streets of Gadgetzan is AMAZING! The characters, the conflict, the aesthetic.
Would love to see it come to WoW, and have Tanaris be turned in to a full urban zone. There are a lot of wilderness zones, and there are a lot of cities in Warcraft. I would love a huge zone where you leave the quest hub area and head off in to dark dirty city alleys were you never know what’s around the next corner.
It would also be chance to kick back and relax the Alliance/Horde thing. The three crime families divided up by class makes for an easy to understand set-up that people can jump right in to. The classes not in Heartstone would need to be added, but it’s 3 for 3 so it’s no problem. Monks to the Green Lotus (obviously), Demon Hunters to the Kabal, and Death Knights to the Grimy Goons. In addition to those 3 factions, you will still have the “Old Town” Gadgetzan run by Marin Noggenfogger.
There would be a huge amount of potential for zone goals and stuff. Boost your crime family NPCs, undermine the others. Sneak over to the wrong side of town and try to pilfer some goods from your competition.
At the very least, I hope some of the Heathstone characters pop up in WoW.
Bronze Dragonflight could shift the caverns of time out to an island if need be.