James Ricker wrote:
That's why the engineers get paid the big bucks to think of solutions for these problems.
A vertical launched torpedo system could solve that problem.
You literally can't pay them enough unfortunately

No there will be no "Vertically Launched Torpedo" system with un-guided era torpedoes.
You may see armored sponson's but to be honest, (despite how they play in "World of Warships") torpedoes as a primary weapon were on the way out by WWII.
Given the nature of the terrain the USSR has to traverse to invade Korea even a 'shattered' IJA is going to have an advantage, especially if the IJN can provide any kind of support. IF the IJA/IJN LOSE Korea let alone China they are both 'toast' back home as by this point Korea was popularly considered "part" of Japan. Worse they can't, (and won't" "trust" a demilitarization and would fully expect a Communist puppet state to be imposed within a year or two so that's not going to be acceptable. (And frankly none of the other "Capitalist" powers, US, UK, France, etc are going to support such an outcome) Russia won't get Korea and the Communist party wasn't that powerful pre-OTL-WWII.
Overall the civilian government which results is going to be a lot less military minded BUT they will be dealing with the aftermath of several decades of military over-reach and destructiveness in China specifically. (Ie; no matter who 'wins' the Civil War they will be gunning for Japan at some point for payback) And it was US support along with other "western" nations against the Communists that Japan's invasion and war threw into trouble so they won't be willing to accept a Communist takeover either. They will still flood the Nationalists with weapons, through Japan if Chang can find a plausible way of doing so.
Yamato and Musashi won't be completed but will be scrapped. (NO plans to fight the US/British battle line means no need for ships to fight that battle) And they will have been taught the lesson of tanks. Japan needs cruisers at this point and aircraft carriers to offset the loss of overseas forward basing. As noted though this is partially a blessing as a less militarized Japan can plausibly cut back on expenditures of high-value single items, (such as the afore mentioned super-battleships) in favor of more utilitarian weapons systems.
Which in itself feeds back into less concern by the US/UK/France over Japanese Naval power as it's been neutered to some extent. Which means those powers can now look to moving assets towards the more 'important' theaters of Europe instead of facing a 'two-front' war at sea. (Now how much that will make the IJN "think" about getting frisky is a question but considering neither the IJA or IJN will have a fraction of their "pre-war" power I suspect Japan will just sit back and let events play out instead of getting involved. Play their cards right and they can be seen as the 'lesser' of the post-war evils)
And despite not being as "Imperial" as before Japan has a lot of advanced technology they can now spend money on AND sell products to a more open rest of the world. (Yes I'm thinking the Luftwaffe might be facing British Zero's over London, why?

)
Considering how much the USSR had to transfer to the East to defeat Japan the question becomes how much can they re-position before Hitler kicks in the door. (Keep in mind that Stalin was confident that despite how well Germany did in the West it would still be unable to invade before the end of 1941 or mid-1942 if at all. This is another reason I don't see the Russians leaving a lot of materials behind them, obsolete or not it's what Russia has at the moment which will be important)
Randy