All I am saying is that a non-motorized infantry division is more like a militia or reserve formation than a true infantry division. They lack heavy weapons (artillery, etc.) Especially in the case of India or China.
The PLA was basically a peasant army. Numerous poorly trained and equipped infantry formations with few heavy weapons. This is quite different from, for example, a Finnish infantry division. The PLA didn't have the industrial base to field infantry divisions like Finland or Austria could. Just picked two non-aligned countries out of a hat.
The PLA had many advantages that armies of that type have over mechanized armies. Smaller logistical footprint for one. Cheaper units to build, maintain, and upgrade. This should be reflected in Industrialization levels. But they were also limited by what they could produce.
My infantry units would be:
Infantry - backbone unit of Industrialized or PI nations (considered fully motorized when built)
Reserve - backbone unit of Pre-Industrialized nations (may be motorized by adding APC brigade or upgunned by adding Artillery Brig.)
Irregulars - backbone unit of Agricultural nations
You may split these units however you want. (NATO, WP, etc.)
Also, with regard to the Transport Helos. I think we may be confusing tactical speed and maneuverability with strategic speed and maneuverability. Strategic speed the rate of movement between provinces. Tactical speed the rate of movement in a province. The game simulates strategic speed and abstracts tactical speed. Increases in tactical speed should lead to increases in organization, morale, etc.
Motorization of Infantry increase strategic and tactical speed and maneuverability because of the across the board effect but the 'helicopterization' of units in this time period only increased tactical speed. These choppers allowed a unit to engage the enemy more effectively tactically in the province of action. The range and cargo restrictions of choppers of this time did not allow for strategic level moving of large field formations (Brigade, Division, Corps).
Even now the 101st with 2 Aviation Brigades still cant move more than 1 brigade by air at any one time. This is the most mobile division in military history. They are tactically mobile not strategically mobile. Once they are airlifted by heavy cargo planes into an area most of the division will drive to the area of operations not be choppered in.
Realistically, a chopper brigade should be a mix of attack and transport birds. It should add to a HA, SA, org., mor., and reduce penalties for terrain (attack, defense) due to the tactical speed they increase.