It's probably been stated dozens of times that Battleships should be able to essentially ignore fighters, gunboats, and to an extent, bombers in combat, while also being unable to effectively deal with them on their own.
Limiting them to a handful of missiles severely damaged their ability to combat each other at very long range, as well as having a go-to tool for dealing with kiting and heavy cruisers. The splitting way back also butchered their ability to actually kill anything that wasn't another battleship. So we're halfway there. They can't effectively kill anything smaller than them, but they're still just explosive pinatas to everything else.
What they need is to be heavy ordinance, and to be able to fill the field between them and other battleships with crossfire that makes a no-mans land.
Despite the severely reduced population however, I'm afraid that'll still be a no go for performance sakes.
