I prefer a BR4-5 Heavy AA option but only 37~57mm ones or the quad Flak, and a rework to AT guns.
BR3-4 got a BR5 heavy AT gun with fewer HE ammo (5 rounds) and normal AP. (for now BR3 use BR1 AT gun)
Or let the dev team get a different AT gun for every matchmaking BR option (and different guns for Italian, UK squads, if available), which everyone would like to see. Only if they can find enough type of AT gun for JP.