To be able to buy a arty support to the GP for a wee perk for instance is IMHO a very good idea.
Say it would be a perk issue with limited rounds, aimed by the GP.
Perhaps fired from the spawn, with the only limit of no enemy GV's nearer than a mile or so.
Really,- quite an idea, and doesn't even incorporate a new vehicle or modelling.
Later on, the Arty could be incorporated. Also that would add some gameplay,- if those driving would get co-ordinates from a spotter.
From RL it makes more sence than Panzer-in-town