Apart from any regulatory issues, and the technicalities of securing a wheel chair to the seat rails, the other major issue would be the requirement for the seats to be removed in the first place...depending on the location, say two, but, more realistically, three for comfort and access, rows. The number of seats would be variable, but, you would expect a lot of airline resistance to removing rows of seats just for one pax, however well deserving their carriage may be.