You don't vault back over a fence to retreat
This is a good point I completely overlooked. However, the whole risk/reward question rarely plays an actual role in gameplay. The vast majority of the time it is very obvious whether a fence should be jumped or not. And if there was an "automatic" vault it could be deactivated on retreat I guess.
To DonnieChan: I just wanted to share some thoughts about a general issue that could play a role if there's a CoH3. That's the only reason I think it's worth discussing. I don't care about CoH2 specific balance problems.
mappers can easily use un-vaultable but still low enough walls
Well, they obviously don't use them as we see in CoH2.