name one spawn that isnt camped? or where airplanes do not fly around? unless you are sitting in your own base shelling another 30k away, you will be at the front.
semp
Considering I tank more a tour then you did in a year, I would know. In a neutral spawn artillery would hold the advantage until the spawn gets broken or the attack collapse.
In 7 out of 10 attacks, I see it broken, unless there is a major push then 3/10 generally can keep the fight going on - in which case you don't routinely have aircrafts flying over the spawn.
6 GV battles today, not one time did my panther get picked up attacking an enemy field or V-base, I say its give or take, adding an artillery piece means you better have a friendly in a wirbl next to you or you will pay the consequences.
so It even's out being BVR and indirect artillery, which also requires someone giving you supplies.
Edited:
Artillery or SPG would not change the balance of tanking, in fact it offers more targets for a defender, considering the limited Anti tank ammunition they carry if little at all as AKAK said. It would be an interesting add down the road, for example if they add a STUG-G (for example) then a H wouldn't be to hard to re-model with a 10.5cm gun.
Just as an example, one reason a stug-G and M4-105 would be an interesting add later on.