This means, in case I set the turn around time too short, the doors will close even though GSX is still loading the aircraft
Let's try to see it from a real-life point of view: would you set up a short turnaround time, if you knew you had to load a certain amount of stuff ? I guess the solution here is to simply select a turnaround time which is long enough to allow to do all your ground operations.
Since GSX never, ever, tries to interfere with the airplane system, there's just nothing we could or should do to fix this. It must be done by the airplane developers, because only them can really know about any possible consequences of changing the airplane state.
For example, what would happen to the airplane internal state if we force-open the doors from GSX (which might seem a possible "fix from our side" ), when they should not be open, for example depending on the status of electrics, hydraulics, etc. ? We could easily mess up the whole simulation, and that's why GSX never, ever, tries to change anything on the airplane itself, and it's only *reading* data.
Many developers understood this and, they are doing really nice things, especially with the next update, where the level of integration has been increased quite a bit. But of course, we cannot force anyone to support GSX.