I think we have to be realistic in terms of what can be achieved within the Sim, and expecting Microsoft to provide a ground service to all taxiing aircraft is really not going to be practical, especially as its obvious that most airfield layouts, while looking similar to the real airports are not completely correct and the taxiway designator are often incorrect.
I think the best that could be achieved at airports would be a ‘Taxi to RW09 holding point B5,follow, or give way, to the British Airways A320’. The current system seems based on the FSX one , and the old railway ‘block’ system, where once an aircraft had entered a taxiway, no other aircraft was allowed to move on that taxiway. This is obviously incredibly inefficient and impractical, but presumably relatively easy to program.
Ground vehicles should only operate on the aprons in proximity to the buildings. In real ife they are permitted to operate un controlled by ATC on aprons, giving way to moving aircraft. They do require an ATC clearance to enter the Manoeuvring area, ie taxiway and runways.
I don’t have a lot of experience of the American system, but I’m reasonably confident that most IFR flights into European airfields are radar vectored for ILS approaches as a matter of course. The really great skill of Approach Radar controllers at busy airfields is their ability to selectively vector different aircraft types, with different wake turbulence requirements, in order to provide the most expeditious approach separations while allowing the Tower controllers to keep up a good departure rate. If aircraft were allowed to follow STAR approaches and then self position on to the ILS the result would be a greatly reduced movement rate. Probably less than half that achieved with radar vectoring.