I don't know wether or not this has already been suggested - I apologize if that's the case.
But, I would like to see the ability to choose which 'route' the aircrafts should take via the taxiways from and to the runway. Normally it's the ATC that chooses that of course, but in case you want to build a bit complicated taxiway system I think it's best if you can then customize which taxiways aircrafts from let's say stand B 11 should take to get out to the runway.
Another one is that the taxiways has names like in real life. A, B, C, D, E etc... Would be nice if you could name them yourself but it can also just be randomized by the game itself.
This was written a bit fast because of life.. So feel free to just ask if there's something you need to get explained a bit better.