I don't want to distract you from ATC-SIM 2 development, but I noticed the line-up times from the holding point (when issuing an aircraft a line-up and wait or takeoff clearance) are very short.
It seems to take between 8 and 20 seconds (there is some randomness which is nice) for a line-up to occur in the sim, however as an A320 pilot I can say from experience that it actually takes around 40-45 seconds from a typical holding point to achieve the lined-up position on a runway, from clearance being issued.
Even with an expedite or 'be ready immediate' instruction, it would still take at least 30 seconds I think.
Not sure if it's a simple change but it would make the sim more realistic. Thanks for considering.