You‘ve brought up several interesting points there.
I agree with The aspect of the big band having a visual live component. I‘ve often had the goal to play „popular classical music“ on synthesizers with orchestral sounds, but really one of the problems why there is little demand for such a form of live music is that a real orchestra conveys a totally different live feeling also visually.
Also soundwise, even a top-notch instrument cannot replace a bigband or orchestra, and one of the bottlenecks I see is the PA system. You would need a very good and detailed acoustic stereo stage, maybe use different outputs for different orchestral sections to come closer to the wide, direct sound of a real orchestra.