Imagine fighting a Goldfish that has an Hwacha or any other ship with guns that destroys heavy gun with ease. How many shots do you get to charge before your gun is gone? If the current push is strong enough to keep ships at bay even in close range, then you don't need to charge them. If the current push is not enough and would be the strength of an uncharged shot then I don't see you being able to charge a shot before it is too late.
I like the basic idea though, it also enables the gunner to outsmart an enemy pilot since a pilot can currently time the shots and active kero/moonshine minimize the minotaurs push force.
Maybe instead of a bigger push you would get more projectile speed and maybe a small damage increase? Sniping components at range with the current minotaur won't happen and on its own the Minotaur isn't much more than a nuisance.
That chargable shot idea could work for other guns too, but it could also lead to a replacement of Lesmok rounds, making the gunner less necessary.
Chargable Harpoons!