I didn’t find this topic. I’ve touched on this idea before in threads about tanks in the gray area.
I see two possibilities
Would it be fair to be able to fire at enemy positions in the gray zone with artillery?
No, greyzone is an anti spawn camping feature. I don’t see a reason why you should be able to target enemy spawn with your artillery fire.
Well, I see that you didn’t want to read the whole topic and choose one of the options, but just said no.
I did and grey zone should be no go, that’s it. There’s nothing worse than spawncamping.
Only with rocket artillery against a marked target as it is dedicated to destroy tanks 
Would be used by veterans (such as myself) to place an artillery strike right in front of the default spawn so that the spawn protection is over and stop any newly spawned troops to advance. Game shows that rallies are often not placed. Easy meat grinding.
I don’t think communication bombardment can effectively suppress the enemy
Unless you are so incompetent that you ignore the bombardment area and keep walking in
As long as you can’t bomb the enemy’s spawn point, that’s fine
Maybe you can circle 2 small infantry and tank respawn areas in the gray zone where artillery fire is prohibited.
I think this can suppress camping in the gray area to a certain extent (even if it can’t destroy the tank, it can still interfere with the sight with smoke)
After all, now, if the conditions are favorable, you can call for artillery fire on the future spawn point, or even a bomber raid.
And the concept of firing at an enemy vehicle or structure in the gray zone, but only when marked?
I think the only way to do it atm is with the 8cm mortars. As long as you mark something then it can be hit. The problem is that most ppl that play this game can’t seem to find the default v key…