You miss two points and i dont meant to be personal now. First one, the game was intended to find flanking options as a main mechanic, in between patches that mechanic was lost or became too hard to pull, so using the "wouldnt people do the obvious logic" strategy is not an argument, since people dont flank because M36 are able to pen frontally and on the move at the highest stock heavy axis tank (Pnter), why would people do something as complicated as flanking and risking their units when a single straigh shot is good enough and no risk involved? Answer that first and then you will know why woulnt people flank to win tank fights if that werent an option.
The game has never been intended to find flanking option more viable, that's the complete opposite. If the Jackson has been redesign to what it is today, that's for reasons and one of them is flanking is a dead mechanism in this game.
If flanking was an option for USF then sherman would have been the tank with defensive smoke to be able to disengage. But nop sherman are design as infantry support with offensive smoke to cover a raid.
If flanking was an option for USF then Axis faction wouldn't have pfaut/engine damage on each of there mainline infantry, like in COh1 which was more flanking friendly.
If flanking was an option, then the attrition (fuel/mp/munition) would need to be much more favorable to USF. You can't expect balance if to destroy a single target as USF you have to engage 2 or 3 of your own with a high risk to lose one or all in the process. While in return your opponent can just site at max range and pickup your unit safely.
If flanking was an initial design then side armor would have their own values and not being a flip coin mechanism.
And we all know what it means if you remove pfaust to Axis mainline infantry or make USF medium immune to their engine damage or change the economy mechanism to be more favorable to USF. Games would probably not last long enough to let you field a panther and see it being flanked.
At the end of the day you can propose whatever you want, remain the root cause: Jackson need to fight Super Heavies, Heavies and mediums with no other support than sherman/scott which aren't able to soak damage.
Ideas around giving USF stock E8 and then specialize Jacksons vs Heavy/Super Heavy have already been proposed since years with no effect. The Devs doctrine here is strong around Axis having tank superiority and it is probably never going to change. Jackson here is just a stop gap for something badly designed from the beginning.
Modifying target sizes impact all factions, that's not a great option since it can invalidate those tanks vs UKF or Soviet.
Giving Jackson different type of amo neither, it just a tax micro to switch target between a Pz4 and Tiger.