This is a bonkers as circular runways. Just because something could be different it doesn't mean there is any discernible benefit or ounce of technical feasibility.
Setting aside all technical, logistical concerns, showstoppers and questionable benefits - airline operations and funding models are fundamentally different from rail ops and funding models. How on earth would this work as an operational business, with O&M, payment collection, investment in the vehicles, infrastructure etc etc
I'm sure I could help the 'French entrepreneur' find a better use for their money....