Hey, fun and a little stupid can be fun as long as one recognizes the little stupid
If one wants to go really,
really crazy, I'd agree with Timothy and bail on 30mm and the like entirely. Shift to a 57mm setup. Spam RAM from the VLS (Block II it
can quadpack in Mk 41 according to at least one brochure), and the
Javelin ATGM is now being tested from the delightfully compact
Centurion expendables launcher. Of course, if you're going to spend ALL THE MONIES on a ship like this in the first place, I'd fully expect
NLOS/Netfires to be resurrected. I think that could be fired from Centurion, as well. Going with the latter approach is somewhat attractive, in that you could have
extremely deep magazines taking advantage of volume deep in the ship, whereas VLS is much more limited by the available area on the weather decks.
The only thing you'd miss at this point is HAIL OF TERRIFYING TRACERS to
visually dissuade pilots from getting close or to rattle them and throw off their aim*, and this use really doesn't require a large-caliber gun. I think 20mm or 25mm might be the right choice in such use. Perhaps something like the
Japanese Vulcan mounts, radar-laid (insofar as necessary) with AMDR and the like. I think they have onboard optics for more precise aiming or quasi-local casualty use. My focus with these mounts would be on a use much like the Japanese incendiary shrapnel round (
sankaidan), but without costing valuable main caliber magazine space and barrel life. Ship, I dunno, a dozen of the things. It's not like cost is an object. Note that modern 20mm ammunition is quite a bit hotter than your average WW2 Oerlikon, with something like 30% higher muzzle velocity. They should push a rather wider effective visual "curtain" than those guns. If you want to hold velocity better, the 25mm round (common to the GAU-12/U gatling, of the F-35 and others) weighs four or five times as much, with that same higher muzzle velocity. I'd expect it to project out nearly as far as 40mm of that era (!!!!).
Anyway, food for thought.
*at this point we're full in a
Final Countdown sort of scenario in which Crazy Magic Time Vortex has sent you back in time to fight the entire IJN by yourself, but no matter...