They did that with LST's and other assorted craft. Howitzers, rocket launchers, even tanks firing. Thing is, the range is too short to do a lot of the things a BB could do, and a BB could provide AA. As far as building a special class of ships, why? Once the battle line from Pearl Harbor was back in business, they had exactly what they needed. Add the other OBB's and the problem was solved without creating ($) a new class of ships.