A steampunk airship might well work. Ever heard of the game Guns of Icarus? Recreating that could be fun, but i think you'll need to fight an enemy of similar nature to make it fun. Not someone like Evvie who can just jump on the ship and attack the crew.

The problem with a helicopter or tank is, the three people would be confined inside this rather small vehicle, doing the one specific job they were assigned (one person flying, the other two firing). An airship gives more freedom.