I believe many of us think of this when we first get started using a scope. I decided to use an off the shelf stand after considering the leveraged weight caused by articulation, something I think is important. The overhead frame would need to be very strong so it would be very heavy or very expensive. I was going to wait until need made the investment worthwhile, however I am very interested. Scope stands used by surgeons have very long arms but look like they would take up a great deal of space.
Ed Webber, the gunmaker extraordinaire, has his microscope hanging from the ceiling. it's in a corner of his shop over a massive concrete-filled vise pedestal. Lynton McKenzie got him using a scope years ago for ultra-fine fitting of parts, etc.
Thinking outside of the box is good, notwithstanding Barry's good advice to ask "what box?", oftentimes good improvements are right in our face, or in this case, hanging from the ceiling. My thought is that it is a tuning fork that can be set into motion with the tiniest accidental tap leading to a shaky image. The man who built and uses this could give us a direct answer? My reservation in the arrangement would easily be overcome by the ceiling mount not being one thin rod, but indeed a thin tripod. You get the good arrangemant, bench free, and also it is a lot stiffer?