I don't know. I quite like the whole supply yard and bought vet dynamic. It added a level of intensity that would build up as the game progressed. Sure, it felt kind of cheap at times, which is why I my suggestion includes an alteration of it, but nevertheless it was well-though-out...
I agree, I'm just not sure about giving a full level no mater what vet, since there is a big difference between vet 1 and vet 2 and likewise vet 3.
For infantry it is: 480/960/1920
I think it would maybe better to have faster vet growth, similar to the PE ability. That way built units are not instantly more powerful, you still have to take care with your units, and are better rewarded for keeping units alive. This will fit better with soviet troops being harder to kill with them gaining their own vet as well.