While I think going with a Gun Destroyer is fine, we may want to start building the battleships first, since they would presumably take far longer to build than Gun Destroyers. For that reason, here is a Battleship design:
[] Class Name: Birmingham Class Battleship
-[]
(Image)
-[] Battleship (Main Battery slots 6, Secondary slots 7, Auxiliary slots 6)
-[] Main Battery (6 Slots)
--[] Ultra-heavy (cost 3) x2
-[] Secondaries (7 Slots)
--[] Light (cost 1) x4
--[] Missile (cost 1) x2
--[] Anti-Air guns (cost 0.5) x2
-[] Auxiliary (6 slots)
--[] Energy Conversion Armor (cost 2)
--[] I-field Generator (cost 3)
--[] Extended Barracks
It has both an I-field and ECA because it's a battleship's job to take hits that the rest of the fleet can't handle. It is light on point defense because that is the job of its escorts
I got the name and the picture from the battleship that replaced the Magellan-class in canon