Why not buff up the Phalanx and add a few more?
That’s not a Phalanx, it’s SeaRAM, gunless Phalanx with a handfull or RAM rounds where the gun goes. It is it’s umm.. ‘air defence’ .
Check out the early battleships.
They had ROWS of small guns along the sides for use against torpedo boats.
Howasabout a half-dozen or so upgunned Phalanx guns per side?