First off I would like to say that this addon has added more enjoyment to my flying both on and offline. There is not much in the way of vehicles that I could think of that has not been already discussed unless you plan on doing a military update. Having said that, I do have a couple of suggestions for the marshaller. Please note that i base these on real world experience both as an aircraft director on shore stations for the US Navy, I eventually ran the line shack for one unit I was with, and as a line rat at an FBO at KBFL in the early 80's.
I would like to see the marshaller bring your aircraft straight out of the parking spot while starting on the ramp and not at a gate. The FBO I worked at had 4 spots in front of the hangar that were "drive through" and we very rarely did any kind of push back unless it was for a re-spot as the pilots, for good reason, did not want anyone moving their birds. On the Naval Air Stations I was stationed or deployed to parking was the same, we brought the bird in to it's spot for parking and guided it straight out of the spot, gave the pilot a left or right turn direction, threw a salute and passed them off to their own devices. Since the marshaller is already wearing a blue uniform with a yellow vest he fits right in on a Navy flight line, the only change to him would be the flight deck "cranial" or helmet that all flight line/flight deck crews are mandated to wear. The tow driver is pretty much the same and would only need the head gear.
As I said I am basing these suggestions on a twenty year Navy career and a couple of years as a civilian line rat. Also, I would like to say once again that I am in awe of this product and I know a few other simmers that are planning to get this when they can, one said he want's in on the fun.