What end controls the AI, HTC server or the staff's system?
Not sure what you mean. The missions are built ahead of time, you can't change or adjust them on the fly. HTC's servers are the host, it's not like IL2 where you can have a remote server or use your own PC as the server.
So it sounds like resources aren't a problem and multiple missions could be going at one time!?
There may be enough resources to handle it, but it's an option we don't currently have. You can only run one mission at a time, you cannot set the mission to repeat, nor the system to automatically launch missions every hour for example.