Salutations All
I would have had the Japanese no so overly supplied with their short range 75mm artillery pieces, i am surprised that the japanese did not deploy in any great numbers artillery guns bigger than 75mm, also that the bulk of thier 75mm artillery pieces did not fire anti-tank rounds and that most of their 75mm pieces had slow muzzle velocities.
Now having said that just imagine this, Japan gains the right to produce the German 88mm dual purpose gun and larger guns (105mm or more) and build them in numbers and then distribute them in their division, i would still use the smaller 75mm guns as rapid deployed artillery but once a foot hold is secured then bring in the 88mm dual-purpose guns and medium and heavy artillery, also that i would invest some time to manufacture anti armour rounds.
Also one tactic the IJN never really explored and that was to let loose their subs onto the mercantile routes and engage transports and other supply ships. And another tactic not used was CAP by their carriers, as far as i know. And in the cold heart of light, no Kamikaze attacks, once a pilot is dead he can't fight another day, 18 to 20 years of development and training gone.
I hope this is good enough for some.
Regards
Roddoss72