What CV guns, Shore guns, and GV tanks need is a range finder.
Range finders in real life had 2 lenses, and they were spaced x amount apart but both aimed "ahead". Now taking what you know about the width, the angle at which they had to tilt in towards each other to produce 1 image (instead of 2 -- 1 for each lens) the math could be included in the gears and wheels that angle the lenses in and out. So when used, the rangefinder will tell you the current range it's "set" to, and you move it until the picture is a single, clear, picture, and you read the currently displayed range.
The AH tanks have these range marks in the turret but it's almost entirely useless because you can waste 10 rounds just finding the range of an enemy tank. There needs to be rangefinders.
Heck, even if you're only mimicking a rangefinder somehow.
Rangefinders were vital for ship guns as well. As it is you can sit in the 16" guns and fire for an hour trying to hit a shore battery, and then at the end of that hour find your ship dead and the shore battery intact. There needs to be a way of finding out what your target's range is, then adjust your range according to that. There are still variables such as height of target (shore batteries are rarely level with your ship, GVs can be uphill or down) and motion.
Bring rangefinders to AH!
EDIT: Heck, what if you only enable distance icons on GVs when you're looking right at them in your zoomed turret view? That would approximate a rangefinder. That doesn't help ship guns vs shore batteries, however.