[Imp]

CB is already good for experienced nations as experience is the major factor that determines if a unit CB fires.
70+ are quite good 80+ I have CB fired on a battery after its first shot, cannot get better than that.

Lets assume experience simulates detection equipment & the training to use it, hence the location of the battery.

Low experience sides in the 60s will hardly ever CB fire unless the other side fires continuous fire missions. AI normally does 2 missions & a break try doing 5 or 6 in a row & your inviting CB fire from anyone.

My guess is this represents things well for most nations poorly trained nations will be ineffective at CB fire as portrayed.
If a low experience side has a well trained CB element its easy enough to replicate. Give the formation a experience boost so it gets 70+ experience.

Should the designers want to add a class to under command, direct, general support they could boost experience & either make it unusable on map or give it a high call time as that's not its mission.
This would probably help the AI more than the player as it would be holding its high experience units for CB fire, something you do already.