The suggestion I have made year ago seem allot easier to implement imo.
https://www.coh2.org/topic/68297/super-heavies-td-overhaul-mod
Instead of messing up with all value of target size and accuracy one only changes super heavies.
The idea is that Super heavies get super size.
Unit that meant to hard counter super heavies get switchable rounds that are separately balance to deal with them with low accuracy high penetration and damage ROF accordingly.
Another point worth mentioning is that ROF for most vehicles is not effected by range. If one make ROF changes with range one can make some unit gain more advantages from closing in.
I had similar ideas to you and the OP as well and spent a considerable amount of time thinking about the tank combat in this game.
COH for the most part is loosely based on Rock/Paper/Scissors approach to balancing. For example Machine Gun counters Infantry. Mortar counters Machine Gun. Infantry owns mortars. Like I said loosely based on Rock Paper Scissors. Now when it comes to Tanks, at least at the end game you have only Tank Destroyers and Heavy Tanks.
The reason for this is because just like the interaction between LMG Troops and Close Range Troops, it is generally better to have LMG Troops in an open field than SMG Troops. Sturmpioneers for example if they manage to get close they can do some serious damage, if they are far they will usually lose.
Medium Tanks are basically in a similar position as SMG Troops. They are not as effective as Tank Destroyers Long Range but even if they get close (assuming they can get close) They are usually almost dead at that point and or aren't much more effective than if they had stayed in long range.
So then the solution I came up with is, Allow Heavy Tanks to flat out Counter Tank Destroyers but then allow for Mediums to Counter Heavy Tanks. So lets take a T-34 for example.
T-34 Penetration
near value="120"
mid value="100"
far value="80"
The Near Penetration is not that much different than the far penetration. If we were to take the Near Penetration and made it say 240 then we could have a similar unit interaction to infantry where:
Heavy Tank = Essentially a Machine Gun
Tank Destroyer = LMG Troops
Medium Tanks = SMG Troops
So the purpose of this is to give mediums a clear defined role instead of acting like a shock unit like the T-70 where it has a small window of usefulness before the Tank Destroyers and Heavy Tanks hit the field and promote combined arms. This is why I had proposed that each faction have access to heavy tanks as part of the core army instead of via doctrine so something like this could be implemented. Also from a historical and realistic standpoint allied tanks had to get close to penetrate German Armor as the guns were not as effective from long distances. It would make sense to give Mediums an SMG Type of role in tank combat.