There's a VGAS proposal out there that would have fitted one, complete with helical magazine, into a Trident launch tube. Capable of firing from persicope depth, only the muzzle would have been above water.
5" rather than 6", but they also said it could be scaled up. Although I'm not crazy about the idea of exposing a submarine just to fire off a bunch of artillery shells. But it also takes up less deck space than 64 Mk41 vls cells, so maybe it can be fitted to smaller ships.
A dedicated monitor design would have been much cheaper and better since it could have been attached directly to the marine unit.
The USN decided against fire support ships in the 60s/70s, but VGAS might make them viable.
Or just add VGAS modules to LPD/LSD ships.
Isnt the problem for the USN that Zumwalt and LCS were designed in a period where there was no naval threat to the US so planners were desperately trying to make them relevant to the real world problems faced by the US from 1991 to the re-emergence of Russia and the Xi change of Chinese foreign policy in the last decade?
Even now it is unclear (especially after COVID) whether Russia or China can really match the USN with all its faults.
Russia has not built a serious class of major surface ship since the Cold War.
China has no naval experience in the modern era and is mainly focussed on keeping its military happy to support the regime.
Part of the problem was the "transformational" mindset that came to dominate the post-cold war era. There were perfectly viable designs, ranging from the bigger Spruance/Tico CGBL (cruiser baseline) design to the 4x64 cell vls cruiser designs Friedman talks about in US Destroyers that would have worked, and could have been DD and CG follow on designs into which Zumwalt technologies could have been introduced as they matured rather than trying to do everything at once.
As to whether or not the PRC or Russia is a match for the US, given the rate at which PRC is building warships there is a one sided naval arms race on and the USN will be left in the dust if this continues much longer. Unless PRC's naval shipbuilding collapses I suspect a combined USN/NATO/SK/Japan fleet might have trouble in 15 or 20 years. The RN took the USN more seriously prior to WWI than we take the PLAN now. I think that's a mistake. 20 years ago we had superiority in their backyard, now they do. In 20 years they may (I'm not saying it's inevitable, just possible) have superiority globally.
The "fiasco" isn't with the design it's with how the USN has handled the program.
I'd say part of the fiasco is having an overly ambitious "transformational" design, but I don't think the USN has handled a program well since - what - the Burke class? Or maybe Viginia? A-12, A-6F, NATF, AF/X, AAAM/AIM-120, Superhornet over SuperTomcat, Zumwalt, LCS, the list seems endless.
FREMM seems a reasonable decision, so long as they keep it simple and don't start changing requirements and adding new ones. Hell, I'd be for Sejong the Greats for Tico replacements, AIP SSKs for surface raiding and supporting the SSNs, Hyuga or Dokdo for ASW helicopter carriers, Cavour's for escort carriers, Sa'ar 6 for convoy escort (and Littoral Combat), Singapore's Formidable FFG and Endurance LPDs etc. We have allies, why not take advantage of their expertise? They use AEGIS and SM2/3/6 and ESSM and MH-60s, we can use their hulls and designs (built here since shipbuilding capacity will be important in a long war). Adam Smith, comparative advantage, and all that.