The Swiss Mod has a Paladin, not sure if it's the M109A6.
AI had some trouble engaging targets at over 1500m but you had range to hit just outside of 1800m or so.
With a bit of scripting you should be able to use it to target at any range, but ranges over a certain distance (depends on muzzle velocity), will always take 20 seconds to hit the target, regardless of the distance travelled.
Not sure if the guys at CoC know a better way around the range limitations of OFP's 20 second shell life span?