Imagine a battleground set in a ruined elven or troll city. Lots of buildings with multiple floors, basements, entrances and exits, maybe even "secret" passages here and there. Roof accesses. Narrow alleyways. Twisting roads. Courtyards where LOS is broken up by statues and pillars. A joint Horde-Alliance archeological investigation into the ruins that went well, until there was an inevitable falling out... just before something went very wrong.
Now the opposing teams of investigators are trapped in the city with the creatures they've awakened. There are wandering elites who really don't care who you are, so long as you're edible. Creatures tough enough and nasty enough that having them pop up in the middle of a running battle with the opposing faction turns into a game of "who can flee fastest?"
Your goal is to rescue your investigative team, and prevent your opponent from rescuing their team. The various NPCs get assigned to random locations on the map - you need to seek out, find, and hold their location long enough for them to finish their work. Different NPCs on the team give different buffs when rescued - increased mobility, increased healing, increased resilience, increased stealth, etc. - but the buffs degrade over time from the start of the match, so your strategy will change depending on the order in which you find and rescue your NPCs.
Once you've rescued a minimum number of your team, you can start the extraction. Call in a zeppelin or airship, and begin ferrying your NPCs to safety, with honor for each one on board when time runs out. When that happens? Big Bad Thing Under The Ruins comes out and eats everybody's face. Or maybe just the elite mobs start swarming the rendezvous areas.
The scenario could be entirely different... I just think the idea of wandering through a ruined city, dodging monsters and hunting the enemy, would be an incredible amount of fun.