What's the purpose of the supply consumption increase for every increase in tech level? What says that newer weapons consume more ammo, need more maintenance etc.? I would say that the opposite often is true.
It may also cause balancing issues. Lower-tech troops should not be better IC-wise.
I think that the only costs of upgrading should be the cost of researching the tech and the cost of upgrading the specific unit.
They are there for balancing purposes, they are there to slow down how fast you can produce newer divisions.
Otherwise you get the snowball effect: you produce lots of infantry, so your practical value goes up, so you get better at researching new infantry and better at building more infantry. So far so good
But, once you research that new infantry tech, you will still be good at building infantry AND at researching better infantry, since your practical value is still high. So by upping the price, you don't produce the new infantry as fast as you did the old infantry.
Which isn't right
How about this: each time you research a new tech, example: infantry small arms, your practical value DECREASES, to simulate the retooling of your industry for the new equipment.
So add a line:
on_completion = -infantry_practical
to the txt file for infantry small arms.
By lowering the practical value, you also add a very realistic and strategic choice:
do I keep producing the same Shermans or Churchills, since I can already produce them rapidly and in great numbers, or do I go for the better M26 Pershing or Centurion, which I can't produce as fast?
This was a real choice the British made, to postpone the development of the Centurion, so they could build more Churchills to quickly outfit their new tank divisions.
