We've gone a bit off from what I originally wanted to discuss. Regardless of how it's done, Japan is an industrial power capable of rivaling Britain at the start of World War II, with a far more competent army.
Well, if you dont want to address the inherent obstacles to accomplishing this, go full ASB. Give them equivalent of T-34s or Tigers and let them roll on Siberia. Wank away and have fun with it.
Lest you think I am being trite, engineering and design often do go hand in hand with production as the experience in production aids the engineering and design. So you can pretty much let your imagination go.