it's a good idea in theory but could prove too difficult to implement properly. it would require a grid map and a view similar to what the guns have, only overhead enough to see where the shells are hitting. few players know how to direct fire in the first place, but trying to direct fire using just a grid map and what can be seen through binoculars would be really tough. if there was some way of getting a spotter in position on shore that would be more effective. 2 guys working in a coordinated effort as gunner and spotter with direct comms could do some damage but, that doesn't happen often...and the spotter is way too vulnerable.
You can count yourself lucky if greater than 50% of the players can read a simple compass, let alone burdening themselves with FDC.
I constantly hear:
"Cons at 3:00" (which 3:00? mine or yours?)
"Cons coming in from my left" (fantastic! which way are you currently facing so I know which is your left?)
"GV's coming in over the hill behind the red barn." (ummmm.... yeah....)
It is rare enough to hear:
(#) of cons, bearing (XXX) degrees @ (xxxxK) altitude.
You know, real and useful information that might actually help.
I just don't see it happening.