As for call in infantry this in general would lead to awkward infantry timings like soviet shocks and guards, lock them behind t1 or t2? or in HQ and unlocked after teching?, means they come too early and are too powerful if you lock them behind more tech they come later then 2cps so not worth it.
Easily fixed with side teching a la bofors/AEC
Or look at the panzerfusiliers locking them behind tech like med truck would force you to give up panzer 2 opening, you could have them at base HQ and have them unlocked once one of the trucks was deployed, but this wouldn't really change the 3 volks opening.
You can unlock panzerfussiliers after calling in the first truck, if you think deploying the truck is too late
And cps are more than just time, they are earned faster trough combat or teching so a really aggressive early game will unlock those cps faster.
being aggressive does not mean having more deaths/kills or capturing of points. CP reliance breaks the BO rhythm, needlessly.
Consider for a minute that all units are unlocked via CPs vs a game where all units are unlocked via teching. Which would you play? Then rationalize purpose of CPs and its nature. A bunch of random things that you cannot control. Why make capturing, combat, and teching generate CPs? Why not healing and repairing and using abilities? (I'm not sure which do actually give you CPs, but the fact that it the list is vague is part of the point) Sounds like a band-aid solution to a problem that could have been fixed more elegantly.