The game is called "company of heroes" where one of the key gameplay mechanics is unit preservation and vet; it takes skill and micro to get it. vCoH tried the vet purchase or upgrade mechanic and I agree with Relic that it goes against this in CoH2. Keep in mind they tried it again with elite troops vet training ability, but ultimately removed it due also in part to other factors such as timing.
I don't want vet to be buyable like it was in COH1. I just wanted to know if it was possible to lock certain vet ranks (vet 4 and vet 5 for example) so that you'd have to spend ressources unlock them.
For example: 100MP + some fuel to unlock vet 4. That doesn't mean all vet 3 units gain vet 4 instantly after upgrading. You'd still have to gain vet by fighting.