It is kind of like Elite infantry in that the early game will suffer. That is when you need to take advantage.
Why would the early game of elite inf suffer? The way I would use it would not be to get grens. The only inf I would possibly vet would be shrek PGs. But more likely I'd just use it on p4's
You wouldn't even need to pick the doctrine until you had a p4, or wanted g43 at 2 CPs.
Especially with G43, I think grens will vet fine on their own. It's the crushing power of vet p4's you want.