That is of course assuming they can tackle the industrial needs to even get one to sea and how relevant naval power would be in a predominately aerial threat. I’d just build more air-ships and expand the Wonderbolts into more a military force, and not entertainment.
Considering Griffon they would need to be pretty heavily laden with anti-air capability to counter Griffons. To my current knowledge, that’s go more the route of the Yamato class.
Preferably though, they may require more Anti-air cruiser than a battleship. I think those can be churned out faster too and mobilized to assure a competitive Equestrian edge at sea.