Comments - kitfox11

From what I know the closest thing you could find to a grenade launch on a vehicle would either be one of the mortar half-tracks or one of the rocket vehicles other than that the only grenade launcher in the game is the British rifle grenades on the assault squad leader.

You know there are grenade launchers in planetside on some special variants of the assault rifles, battle rifles, and carbines that can have an under barrel shotgun, HE grenade launcher or a smoke grenade launcher. here is a link to to it on the wiki Planetside.wikia.com

You could just set up the lower parts of the bunker to behave like a garrison able window like how people put snipers in a tower.