i've never really done much with my warp editor, so i don't know if this is possible or not.
could a map be made that includes underground tunnels? the vietnam mods could certainly benefit from this, but i think that an island with a huge network of tunnels and chambers beneath it would be great for anyone.
just think: you and your team of special ops guys going beneath enemy fortifications, ambushing the enemy in the darkness, or just the fun of having a map that's really two maps.