Hah - ok I'm going to copy paste some of the things I've suggested in here. I prefer discord because it's easier to chat in real time. Forums are so ... outdated
1.I would recommend there is an info screen for the allies in the beginning of the game where you tell them to USE the Burma road from the convoys interface - maybe even tell them to transfer as much as possible from the US to AUS - Then AUS - RAJ - UK to RAJ and finally RAJ - 50% to China because it needs as much as it gets in 1942 when China is the most obvious target for Japan.
2.My opponent was VERY surprised that to upgrade to weapons 1 on a Chinese corps it costs 130 MPP. That is in both our opinion TOO much. My suggestion having played some WaW and a bit of the new game. I understand that historically China had the numbers but they were VERY poorly equipped. So immo you could MAYBE have weapons cost a bit extra as opposed to Japan (so maybe 80 MPP per tech level? ) but make it so the base cost of a corps is 50/60 MPP. So a new unit shouldn't cost more than 130/140 MPP. Couple that with more events where corps when they get killed they get spawned back somewhere in the back with only 3 strength and no upgrades - Just like in WitP:AE.
3.Bug for Japan - it seems that if you move units that touch the limits for the communist units than Communist China is very angry very fast - after the first turn they got to 88% mobilization. And i did check and i respected the boundaries from the info text - Here is posted a screenshot of the map for that turn and Jon checked the hexes again and found out the bug.
4.Another bug - as Japan i conquered Burma and my opponent built up the Ledo road. He told me that it doesn't work ( i did not conquer any of the Ledo road hexes just to experiment that is works or not). Might want to check that as well - same as the point from before there seemed to be a bug with the road and should be fixed.
5.No other bugs noticed BUT you must think of a way to balance China a bit more. I found it VERY easy to just overwhelm China in 1942 with all of the air i had. Once i conquered the historical holdings by June 1942 - i could use all the medium bombers to just Rofl-stomp China into submission - i had the railroad to Indochina freed by August/September 1942 and i could have pushed over the mountains and crushed the Chinese - but i stopped in a temporary truce because my opponent had almost nothing to stop me. You could say it might have been a difference in skill and you might be right for i do feel that after Japan takes the obvious conquests and turns on China there isn't much China can do and it can fall very fast. Once Burma road is cut and the mines / production in the south is conquered as China you are kind of dead - considering your weapons upgrades are costing 140 MPP. Apart from my suggestion from above with how you should maybe make Chinese un-upgraded units dirt cheap (so he can build a lot of them fast and just let them entrench in the mountains). I don't know what other suggestion i could give - Maybe have China start with 2 engineers so they could also start more forts?
Then i suggested some changes on how partisans work based on how partisans work in the USSR in a mod by Lothos called TRP. In said mod you also have partisan spots that need to be garrisoned but there are also random partisans that ALWAYS appear (roll based but you cannot stop them) so that would force Japan to keep both a garrisoning force and a policing force.
Another suggestion i made is considering naval combat because unfortunately it always devolves into swarm vs swarm - I would cut in half the number of the ships for both sides AND also cut in half the damage remaining ships do. As you well know a task force was usually composed of 2 ships of the same class (2 BB - 2 CV etc) with escorts. So that wouldn't be that unrealistic. There is a naval mod in one of the vanilla games ( WiE or WaW) that you could take inspiration from in order to reduce the number of naval units and make encounters more realistic and fun.
Lastly i was asked to give my opinion on research and i've wrote this to him.
1.First thing that hit me was the limited research that Japan can do. I find 1250 MPP too restrictive BUT on the other hand i only have 1 PBEM game so i couldn't say how this affects the mid/late game. But i would at least bump it up to 1500 MPP to give Japan more options.
2.Inf Weapons - It's fine as what the upgrade gives but 1/5 is too much. The problem that i see is that Japan with a bit of luck could get ahead on this and get to 3/4 in 1944 while western minors/China would be stuck on 2 - and then the Experienced + Upgraded to lvl 4 Jap corps would ROFL-stomp the western minors. I would maybe make it like China gets a max lvl of 1 - Japan and Western Allies minors (India/Australia etc) get a max lvl of 2 and USA/UK max lvl of 3 (or maybe keep it 2).
3.Same with advanced tanks. China should be on max tech 1 - Japan max tech 2 (since they really didn't have good tanks) and the western allies could go to 4 (not 5). To streamline the game a bit better and make it a bit more action - not sit around and upgrade to the next tech.
4.Single Engine Aircraft/Four Engine Aircraft - fine as it is. I love it.
5.Fire Control Radar - I'm mostly ok with it - it should also give the BB and DN same bonuses for CC (or higher even).
6.Advanced Torpedoes - 5 levels is too much immo - make it max lvl 3 - and also make Japan start with a lower level of torpedoes - 3 is too much - Jap subs really put the hurt into allies ships with that lvl 3 too early.
7.Advanced Subs/ASW - works fine with torpedoes and also balances off ASW so i have no problems here.
8.Art Wpn - i would restrict the tech lvl to 1. Level 2 is making arty a killing machine. Or halve the bonuses and keep 2 levels.
9.Search Radar - Interesting concept but i would put this in the passive column and replace this research with Fuel Efficiency that is upgradable on ships (all surface ships that is) to give them more AP per lvl and maybe the evasion % from the search radar.
10.GAW - very good especially limited to 2 levels otherwise the air force becomes the finger of God.
11.Supply Depot - very nice - love the upgrades to aux units.
12.AA - it's ok. Maybe make it max lvl 4 ?
13.C&C - OK.
14.Ground Warfare - Very nice - love the separation for both sides.
15.Air/Naval Warfare - Same - love the separation - maybe make this 2 levels as well?
16.Amphib Warfare - Ok.
17.Submarine Warfare - submarines get OP very fast in this game. Limit the tech to 2 for Japan and 3 for the US ?
18.Naval Construction - novel idea - i love it.
19.S&I - classic.
20.Logistics - classic.
21.Prod Efficiency - Considering the .5 increases make it cap at lvl 4 for more consistency otherwise i like it.
22.Industry and Manpower - Same observation as above. Maybe limit it to max lvl 4.
Final Thoughts - Research works fine but maybe you could try a different approach. How about you double the max MPP that can be invested into research BUT you disable double chitting. This way research can get a few spikes of good luck but you won't see 4 engine bombers researched at maximum at the end of 1943.
Happy Mr. Tanaka?

Feel free to contribute. Me and my opponent enjoyed the scope of the mod but it needs a lot of play in order to make it more balanced in our eyes.