To be honest Japan would make a very interesting faction to add and will bring some unique faction mechanics to the table
Italy could also make a unique faction even with German support but Afrika Korps is gonna be the bland copy paste weapons and tanks from Wehrmacht and OKW again which for the Axis is starting to get boring
Japan would bring something fresh to the table and with Americans and Brits fighting alongside Soviets,I&R StGs, Pershings, Comets many people wouldnt mind Japan being added with some weapons/vehicles that saw little to no use fighting alongside Germans
with Japs faction look-a-like i'd go like this:
(faction mix of ostheer, soviets and OKW)
HQ: Engies (standard 4 man, rifles), Rifles (5 man, rifles, some nade, AT nade, upgrade with LMG or SMG)
T1: MG, mortar and sniper
T2: light AT gun (37mm i think), AT rifles squad (some 5 man with semi-auto AT rifle) and some 222 alike vehicle but with no 20mm cannon but with MG's (forgot it's name)
T3: some mix of light tank, tank destroyers, HT's and early med tank - light tank like Ha-Go, TD like Ho-I (like SU-76 but with better penetration) med tank like Chi-Ha
T4: since brits got Comet that never fought in WW2 then why not give somethink better to japs - some standard med - Chi-Nu, heavy like Chi-To. some arty stuff, so SPG or rocket SPG, maybe SNLF squad
call-ins and other stuff: 150mm mortar, 75mm flak (similar to flak88 but with worse gun) flame tank (with 5 flamers around it), some SPG's or other arty types, Ha-To (which is like Sturmtiger on halftrack), some elite infantry
Japanese faction would be tbh the most interesting army in terms of combined arms, firepower and flexibility
Overall its a good army design Barton, I wouldnt mind Japan being added with something similar to this
But question for you and everyone else, who would want an Anzac commander for Brits and USMC commander for USF if Japan is added
I dont know much about Soviet-Japan conflicts in WW2 but they could get a Pacific commander aswell