Wrecking a PZ4 with a Jackson with max range shots on the move isn’t balance, it’s garbage. At max range TDs/AT guns should’t have as much accuracy vs mediums, thus it would require you to either get a lot of shots in quickly, vet up your units or get closer, which would get rid of the current stagnant TD meta.
Getting shots in at max range requires a lot of spotting and direct LOS, this is hard to achieve, especially if you want to chase the enemy medium tank. If the allied player can pull this off, he deserves to do the damage. It's only easy to get long range hits in if the enemy is using their medium tanks as frontal assault break through tanks and their understanding of flanking is 'rush at enemy and try to blitz behind them'.
Honestly I think TDs are fine as they are. Only the JP4 feels too weak with penetration compared to other TDs. I would like to see it get a bit more punch in return for a nerf to the bullshit phase shields it gets that make the tank literally invulnerable if you hold fire.