Is this actually feasible though? I would have thought the operational cost would be prohibitive and airport to airport not really that convenient to make it worth it. You could charter a helicopter for not much more and have more direct access around major cities. Then you still have to get the public to accept getting in a small single engine aircraft on a regular basis. You won't get the big corporates as their charter insurance requirement usually stipulate twin-turbine multi crew.
The second video discusses the single engine 135 certification at the 11:15 point, if you want to skip to that.