So your mod is friggin' cool, you get from "basic area-saturation" to "precise-targeting", now I challenge you to make a third tier, which calculates the smallest amounts of shells needed to destroy all buildings in a given area, obviously calculating the best targeting points xD

I like that idea - it's a bit of a geometry problem to efficiently calculate explosion radius coverage and place the shells overlapping as many target structures as possible, but I'll look into getting something like this working.

The radius is a property of the shell used, so if a mod adds a smaller or larger area shell (and especially in mixed shell scenarios) this is unfeasible to calculate.

I would imagine that it would be reasonable to have (ideally) a per-force (per-map or per-player) configuration for 'blast radius of artillery ammunition', on the assumption that all artillery will be loaded with the same ammunition (presumably whatever gives the biggest bang). If they aren't, this makes manual targeting equally non-trivial because you don't know ahead of time what shell is gong to be sent down-range when you use the artillery remote.