Well Damage to Fire Control and Rangefinder systems, define system! In a WWII tank isn't Fire Control just the sights nothing more nothing less? vision slits and prisms can always be replaced by popping ones head out of the cupola I guess? The gun sight is usually well protected behind the mantlet looking through a golf ball sized hole anything less than a direct hit will have no effect. Schrapnel from a near miss has to travel up from the ground so the h ull of the tank will block it. Basically the sights are internal, so safe.
WWII tank rangefinders are very rare those tanks that have them have them mounted on the roof. Again the tank body will protect the instrument from blast and scrapnell unless the shell actually lands on the roof. What is the chance of the shell landing on the roof, about zippo.
Look at figure 4 from
http://nigelef.tripod.com/errorsmistakes.htm
Figure 4 and 3 show that the game 25 pdr dipersion over about 7 hexes is about right at 8000yds, notice the modern gun 155 mm FH70 is much more accurate, look at the dispersion of the 6-inch Gun Mk 19 you would be lucky to get a shell to land on the map!
So comparison of ww2 guns and modern guns is misleading. Modern guns shells are landing in a much tighter group. Chance of a direct hit or near miss using WWII ordinance is negligable even with observed fire fig. 3 shows this for a 25 pdr. In WWII As already pointed out, direct hits only result if really big numbers of guns are committed. If direct hits were as common as they are in the game in real life then the many open topped vehicles would have had a lid put on, quick smart.
Help on RF and FC I find confusing, Range Finder is about range finder, OK, but help also says it is about the gun sight. Shouldnt sights be part of Fire control? if not then what is Fire Control? Help just describes the effect FC has not what it is. It would look much neater to me if RF was RF and FC was the gun sight. After all Stabiliser is Stabiliser, Accuracy sits with the Weapon. What is left to be in FC except gun sight?
Personally I would move sights out of RF into FC, leaving RF for RF. RF value would be then be 0 or so for most units and those units that actually have a RF would get the appropriate value.
FC could be related to sights magnification, bigger better, and possibly sight design. The fineness of the traverse and Elevation gear is relevant but no doubt too granular for this game.