Artillery was in its infancy where it belonged. Now we got base barraging and random one shots anywhere on map. This is quite serious and will only get worse when the british arrive. I agree with your changes though we share the same opinion of what needs to be done. Though no less than 500 mp.
Back to brits. They get 2 howitzers inside their base structure. So unless this is changed (likely will no be) unfortunately artillery and off maps cannot be disabled for good when trying to target a base.
Dude, those two 25 Pounders are just, for good looking, because the King liked them.