Thank you!
At the moment we have no such system but of course we are open to implement in the future. We did some tests with line up and wait but it did not work so well with the current ATC system. Especially balancing a busy approach. The system now only allows one aircraft at the time to enter and operate the runway. So it is currently on hold.
Yes, the takeoff would have happen as the holding aircraft “checks out” the runway once reaching an exit/holding point. In that case he was holding because the taxiway was busy in front of him. It is extremely complex to build a flawless ATC simulator, there is a reason it is still operated by humans as there are so much coordination involved. Translating that into code is difficult. If we were only building an ATC simulator, we would probably have all those things implemented but we have the passenger, vehicle, baggage which also have a lot of rules that needs to be translated to code.
I hope that answers your question. 