If you are able to design one that passes all FAA/EASA/CAA/<aeronautical regulatory body here> certifications, I think ALL airplane builders will hail you as their saviour. Not to mention the airlines ;-)
The seats sit on rails on the floor, so they can be swapped out or repositioned quite easily. Usually the Supplementary Type Certificate for each aircraft plans for this.
While being true, not all Seat configurations are automatically approved for operation. The swapping itself can - as mentioned - be performed overnight.
