Another idea that came up on discord, that I've considered in the past, was "Volcano but with the map boundaries turned into water".
Here's an example of that which is just lazily taking the original map, deleting a bunch of the terrain and making the outermost edges all dip to the same elevation. A real version would be a bit classier than this. So we get our first full combined arms map - infantry, tanks, helis, planes and naval - and isn't particularly big, so in addition to travel time not being a concern it could even be suited for low player counts.