This has been asked and answered many times on the forum, and we confirmed is under consideration but, it's quite an extensive change, that can possibly break existing GSX add-ons and airplane integration, so it's not a quick change.
The recent addition of time delays for Boarding/Deboarding, would help in many case where you wanted to separate the baggage loading because, with a delay, passenger or crew would board later, but baggages will start loading immediately, which is usually what happens.
