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Well, the Vaos were put there for a reason: to prevent diagonal attack on the Falcon and Eagle (flying R and Q) behind them while the latter have no room to move yet. The Interactive Diagram estimates the value of Falcon and Eagle similar to Lion and much better than Amazon, respectively, while the Bat, which could make such attacks, is estimated as weaker than a Nightrider or Dragon King. E.g. 1. l7 followed by 2. ARi6 would threaten 3. BAp9, gaining more than the value of a minor. (Or BAo8 after protecting that square, to gain more than a Queen value.)

I understand the principle of not allowing the Vao to quickly trade itself for something more valuable. I always considered the hoppers only about half as valuable as the corresponding sliders, which would make the Vao worth much less than a typical minor. If I should believe the heuristinc of the Interactive Diagram, the situation is different on 16x16, though. (I have no empirical values for 16x16.) And this stands to reason: the Vao (as well as Cannon) is an unlimited-range piece, and the value of such pieces should go up with the board size relative to the short-range leapers. According to the Diagram the value of the Vao is about equal to that of Knight, Camel, Zebra, Elephant, Frog.... (The Bishop, being a slider, is of course worth much more.) So there is no advantage in quickly trading a Vao for any of those.

On the contrary; the Diagram estimates piece values at a total piece density of 25%, and the value of hoppers tends to decrease towards the end-game. So in the opening, with a piece density of over 50%, the Vao would probably be worth significantly more than any minor, with the exception of the Bishop. This is basically the same argument as why it is bad to play 1.CxH in Xiangqi.

So I think having the Vaos hitting the opponent camp in the initial position is no longer a problem in a variant this large. As long as there aren't many very valuable pieces directly behind the Pawns.