What is wrong with...
1- New faction don´t rely as much on Call in tanks as EFA.
2- Teching cost and opportunity differs greatly with OH, a bit with SU and mostly nothing with USF and OKW.
Neither of them have an expensive mp/fuel cost for what they get. As USF you get units, as OKW you get utilities. It´s "not optional" not getting 2 trucks and it´s not as a heavy drawback getting a major. Compared that to going BP2+BP3+T4
Increasing the CP cost on callins based on current performance is probably the easiest solution.
That's the core of the issue after all:
It's simply too easy and cost-efficient to hold out until callins are unlocked.
So make it harder to hold out. The mechanism for that is already in place.
And we are still on the same meta. Stall with "lower end" tanks, and then go Callins. I´m fine if this was OHvsSU and USFvsOKW. But this is not the case.
It´s been for a while that either teching diversity (T3-T4 overlapping units for soviets and the design of "not being" able to field both) or cost/performance (OH teching/units) are some issues.