A map that takes place in some open sea.
Throw some carrier groups in and you have a fun scenario for naval fans.
edit #1
potentially multiple maps.
- Pure ocean map, no islands
- Map with some islands to fight over
to win you sink enemy carriers (or whatever other capital ships are added to the game) instead of blowing up their factories or airbases
As for resources, perhaps capturable oil or mining rigs to supply a team money and spawnpoints on the edge of the map to represent new allied ships arriving in the area.
end edit #1