i always in mid 1942. thinking on a another last level infantry (3); to the japan only, because for germans and british if they get level 3 its a must that you need in the game another last level for thanks, level 3 infantry for germans and british is not good, only for japans i think.
level 3 of germans at 1944 its giving the victory to the germans, there are about 25 German divisions
money thats what they must cost a lot if level 3 for example 150 points (dont know exactly) to upgrade level 3.
think that it is in the game level 3 for many many units: by, researching levels of aircraft ground combat
the game is balanced very well, so if you want to change the research area, (great) more upgrades but it has to cost high money what you have already done in the game, so if possible anther extra-level for infantry because you have level 2 at 1942 and of course 4 more years for the infantry
the supply is one of the best thing of the game, its a question of how many HQs do you get, so again the game now is A+ so if you want another +. dont touch anything, just the money, to get what is not now in the game just get money and maybe you can get the new levels
and what is need to get more money (PPS)? only the developers know how to do it
so more PPs (money) it might not a good idea to get that, level 3 (also at ships) but its the best balance.