I'd honestly think adding side armor the way everyone thinks it should be added is actually a bad idea. It would be unfair to add side armor if historic tank ranges and armor angling weren't added as well. Being realistic I can understand how those 2 wouldn't make much sense either. So even though I realize the front half and back half system is also bad my suggestion would be to make the tank armor hybrids of both ideas.
Reasoning for this is so tanks shooting at the front corner of a tank don't penetrate when hitting the side of the tank at such an extreme angle from the front that it would be silly for them to pen. Also considering how much simpler it is to close the distance to tanks in this game and the fact that front armor can still be penetrated by any gun. Even in situations that they shouldn't. (Ex. T34/76 shooting at King tiger frontal armor).
There is a mod I've seen on here that is working armor angling into the game, which is a cool hack considering its a mod and the base game doesn't seem to support the stuff by default. IMO the game is small enough in scale for armor angling and side armor to be factors in penetration. Particularly for the smaller scale game. I think that this might be a good testbed for whether or not it works in a coh type scenario although obviously it will depend on the quality of their balancing too.
In a CoH3 scenario I would be in favour of increasing tank ranges, but not dramatically. Like 60 range default, 80 for TDs and AT guns or something like that. Mainly because the distances are SO short that they are often irrelevant in practical scenarios. My main bugbear is infantry AT, which is only somewhat shorter range than the tanks they're fighting. In real life a Sherman could easily engage targets at 600-800 meters, while a Pscreck has an effective range of well under 200m. And some fausts only working effectively to 60 meters or less. This would all feel a bit less weird if you had slightly more room to differentiate these ranges with. But not so many that infnatry are totally worthless. It's a balancing act obviously but I definitely want to see slightly longer ranges. Acutally inf rifles and such could use a small range boost too for similar reasons!