The fundamental issue here is that tech units are not efficient at all for their cost compared to call-ins considering the length of an average game when you add in the sunk cost of tech. Currently I can spend 200+160+320=680 manpower and 55+30+115 = 200 fuel to get a PIV, or I can get a Tiger for 640/230 that is usually just as powerful as two PIVs and far less likely to die to being outmaneuvered than an individual PIV. If I go for the PIV and my opponent saves for an IS2, I'll in all likelihood lose unless I can gain a huge advantage with the PIV in the 5-ish minutes it gets to be on the field before the IS2 arrives. While if I go for the Tiger, I'll be evenly matched with my opponent once the call-ins arrive, or ahead of him if he decided to tech instead.
I do not think a single call-in unit is in any way cost-inefficient compared to base tech required units right now.
Ye, at the moment the call-ins are to cost-effective compared to the regular ones. But IMO the problem with company of call-ins is that the time between building tanks and callingthemin is to short. Maybe its better to just adjust the CPs again so the time between building and calling them in is longer? That would allow a bigger timeframe for medium tankbattles.
A need to tech/build isnt certain to change the meta, it could be company of call-ins with a building.