So yes, the basic concept works. It is really just a few clicks from FBX to MSFS and if it will incorporate Mixamo, it will probably take any. The dexterity is pretty incredible and the rig and weighting is accomplished by setting 5 markers; wrists, elbows, knees chin and crotch. From there, the software rigs the model and applies pretty decent weighting, there is some sausage look at the elbow, but check those fingers.
So Mixamo is an option, another site I found during my research was "
pixcap." This site will animate, or pose a 3d model, based on a 2d still image, or video. It's not free, but it's pretty interesting.
Thanks again for showing the way, Christian. I wanted to mention the ModelBehaviors section again, because you'd mentioned controlling the models. All of these current models use the abbreviated XML you provided and thanks for that. But the behaviors section syntax looks fairly identical to the visibility parameters of FSX effects. The control variable, "E" is set to time in seconds and it represents duration. the other variable "A" would be an external, or environment condition and that is set to ambient. You can see that the duration can be changed, or set to a specific interval and the ambient condition could be set to one that is, well, more conditional. For FSX effects, we could bump these decisions up to a "controller effect," for controlling complex variables and this may apply here, as well. The entire section could also be completely ignored by the sim, but it's something to consider.