The build times are really besides the point. It is fully possible to have historical IC (Industry/ GDP) if the game includes more factors, the most important one; defence budgets. The United States should be the historical IC powerhouse that it was. But this does not mean that the US should have 50 Battleships or Carriers. This is solved due by introducing a realistic logistics part of the game, where the US would need much of it's manpower and IC to be able to field troops in the pacific and in Europe. Spending would also be limited before the war starts, as the public have little sympacy for high defence spending when the US appeared not to be under a serious threat.
A better AI would also help, so Japan uses it's troops more wisely, and not stacks them all on a remote island. For China's part, troops would use much less supplies and be cheap to build, due to a string of factors.
- Troops deployed on own soil (no trucks, men, infrastructure etc. needed to transport supplies to the troops. They get food from nearby villages.)
- Little heavy equipment (Infact, most of what's needed is ammo and rifles, which is cheap and easy to manufacture with few large industries, and even in local workshops. Some where also supplied from USA and the Soviet Union.)
- Low level tech (No fancy electronic equipment, trucks, tanks which would require a lot of industry to build.)
China would have the capacity to build hundreds of divisions, but almost no aircrafts or battleships.
This is all possible with historical economies of the respective countries, it just needs more variables and fine tuning than what was present in HoI2.
