Map: Something in the flavor of the game mode I listed below.
Game mode: Cap ship battles/assault or shipyard assault/defense.
Alternate game mode: Toning down gunships and battlescouts.
I think one of the things is, if they would give us different trays, each tray could have different rules. So you'd have your hangar for game mode A, your hangar for game modes B and C, etc. This could allow the game to launch a game that is "scouts only", using the tray you can only put scouts on, for instance (and if you didn't, well, you wouldn't get that queue pop!)
I mean, FPS games have a LOT of variation that we don't see in GSF, but much of it would apply. You have the idea where one character is supercharged and the enemy team gets a bonus for killing him, you have the idea where bases are established and meaningful (and several variations on that), you have capture the flag (and variations on that), etc. We don't see any of that in the current game, but there's space for all of it.