Please correct me if I’m misunderstanding, but at least for 3ds Max, Blender, Maya, their Python integrations make this sort of thing as simple as launching the proprietary Python interpreter (mayapy.exe, maxpy.exe), with consideration of a few limited proprietary details. I think Python is just very well suited for this.
Good question, there were already 2 tools out there that do the same as what I now did, but not with the same kind of UX (they didn't look like a usual shell). If Unity sees there's a lot of interest in this, maybe they might integrate it, let's see.