Uh, the Jacksons mobility means it requires less micro, not more. It can easily escape a sticky situation in a way the SU-85 and JPIV cannot.
Define 'sticky situation'.
Encountering single shreck volk?
In every single other case, its fucked because of its hp and its not as mobile as you claim it to be.
Making the Jackson literally the most cost efficient best tank killer in the game that also comes in roughly the same time Ostheer first gets T3 would make Axis medium armor more rare, not less. It would also turn the Tiger into a joke, since the Tiger would be helpless if it's armor was getting penned every time by a tank it couldn't even touch.
God forbid the one army with NO heavy tanks, NO super heavy assault gun or tank destroyer, NO effective AT gun or handheld AT, NO heavy at gun, NO mines of basic engineer troop and least reliable vehicle snare which also requires vet would have a vehicle that allows them to fight all the heavy armor that is being thrown at them.
No, that would be total imbalance.
What makes the Jackson ~okay~ versus heavy armor is the trade off of damage versus pen, meaning that when you pen you fuck a tank up hard, making it's damage reduced but giving it garenteed penetration would mean there is literally no trade off.
Except low durability, armor unable to deflect anything, nothing that increases its sight, nothing that would be able to create buffer zone between it and its target, allowing army for its protection.
You see unit, but are completely blind to the army.
There is a reason why every single USF player who expects late game goes for airborne-P-47 is not an option, its something completely mandatory in dealing with heavy tanks of axis.
While 240 long range pen would be an overkill, it does need penetration buff.