Seeing as we're getting a spotter aircraft, I think the time is right for some artillery to be added. Perhaps the 15 cm Kanone 18, and the 155mm Gun M1.
With ranges of 15.2 and 14.4 miles, respectivly, these guns would be sufficently ranged to hit any base from the spawn, yet they would lack the ability to shell a target from a friendly field in 99% of the situations. To put things in perspective, their range is just a bit over 1/2 of a sector (15.2 and 14.5 miles, compared to the 12.5 miles that would be 1/2 of our 25mile wide sectors)
They would recieve a modified land-gunner mode, that would have an area of variance about the size of a town (if possible). They have to manually adjust fire to be any more precise with the targeting. This means no spawn-camping with a 155mm from BVR without a spotter aircraft (vulnerable). But it will still let them be accurate enough to carpet shell a town without assistance (about the minimum they can have, and still be usefull in groups, since spotting the shell fall of multiple guns is difficult to do). If he clicks on another spot inside that area of variance, it aims at a different random point within that area.
Another option is to give them a land-gunner mode that displays the range and bearing of a selected point, and they then have to manually bring the guns to bear on that target. This would be more accurate against a specific target, but it would be more time-consuming and carpet-shelling would be less effective, since he has to manually adjust the fire of the gun.
They would spawn from the VH of course, and would have a truck or artillery mover attached to them. Deployment of the gun could take several minutes, or be adjusted as HTC sees fit. Ammunition would be limited to 20 rounds without resupply.