That would be crazy op. Scaling ok. But turning basic infantry into elite infantry at vet 3 is batshit crazy. ^^ I do appreciate new ideas but you are loco my friend 
I can appreciate the fact that you might not like the idea, however; I'm not sure how you can dismiss a concept as "Batshit crazy" after pondering it for less than 1 minute. Maybe, I was not clear enough in explaining it.
I'm suggesting that an individual conscript that has reached vet3 could be upgraded into a different class. That's kind of what guards were in real life; veteran units that were awarded the title based on performance. This would not be automatic, a player would have to choose to do this and would have to pay for it.
I am not suggesting that guards or shocks could be built instead of conscripts or that you could upgrade any other unit other than that 1 unit that had reached the vet requirements.
It typically takes +10mins to reach vet 3 with a conscript which is well past the CP requirements to call in either shocks/guards. From a timing point of view a guard/shock units arrival would be no different than calling one in.
If it means that in the late game, all your mainline infantry is something other than conscripts, well that's kind of what ends up happening now.
In my humble opinion, the Ost-soviet early game is great; conscripts do just fine. The OKW matchup can be problematic, however thats more to do with the OKW not conscripts.
That being said, maybe I am not seeing something. Why do you think that this is not a viable concept?