Here is a game concept I thought of a short time ago,

'Delivery'

Each team possesses crates they must deliver to a recipient (smth like a Hermit in the mountains, within a sky island, deep down near bedrock).
The first team to deliver all their crates to the Hermit wins.

Details:
Each team starts with 1 crate each. After each delivery, they receive another crate to deliver.
If a team loses a crate (it becomes stuck, falls into lava, is otherwise lost) they can return to their base to request a new crate for a cash penalty.
Maps will be more-or-less mirrored with the Hermit in the centre. There should be asymmetry however, ie: paths going through the enemy team's side of the map to encourage battle.
Maps should be fairly difficult to traverse; the only flat area where the crate can be easily pushed around should be at the main base of each team. Imagine terrain with sharp mesas, lakes, and cliffsides.
Crate delivery should be possible via airship, however, the hermit should not be in so simple an area that can be reached simply by flying directly to him.
Crates should not be deliverable via the Clonkonaut's cable-transport system. Once the player had a path in place he could deliver all his crates within seconds, so that's a no-go.

Feel free to post suggestions/critiques!