Now that developers are including interiors for their airports in MSFS, I would love to see passengers actually moving around in those terminals, and making their way to the jetway/bus, and into the plane, rather than just spawning at a jetway.
For the MSFS version ( although the feature will fall back to P3D as well ), we added a new feature which we used in a couple of our airports ( KORD V2 and Basel ), which in GSX are called "Airport Walkers". Previously, it could only be used by us, since it required programming their path in the Python language, which is what most of GSX is written into. However, it wasn't possible for users to access it.
Now, with the MSFS version, in a way similar to the Passenger Walk-in path editor shown in the latest Preview we released yesterday, it will be possible for users to define paths that passengers will walk freely, as loops, independently from the GSX actual Boarding/Deboarding process.
This still requires lots of editing, but it's now available to users as well, with a graphic editor that can place waypoints that can also be 3D, so you might allow passengers to walk stairs or take elevators, if the airport you are enhancing has them.
Having something entirely automatic is another issue altogether. Keep in mind that, even in games that "looks" AI-based, like GTA or Cyberpunk, there's still behind the scene the concept of waypoints that tells the game what is a road and can be used by AI characters and what isn't. And there's the concept of "areas" as well, were AI might form in clusters, playing some kind of interaction animation, that's the most common ways to populate game environments like large cities with AI people.
However, in all these cases, the whole scenery is in complete control of the game developers and, regardless how large the map it is, is VERY limited in size compared to what MSFS has, if you add together all thousands of default airports and 3rd party add-ons as well, nobody could foreseeably place waypoints for walking characters everywhere, so we can only provide with the tools, but it will up to users and the community at large to enhance the airports they are interested in.
Surely, shortly after the release, we'll add all these things to our own airports. If 3rd party developers are smart, and realize how easier is to use these high-quality characters compared to how hard normally is to add them to an airport with any other method, they should start offer GSX profiles together with their airports.