Sides of the pool act as beams and if you ribbed the bottom to act as purlins transferring loads to beam it would work. Put ends of beams on sliding bidge bearings and the other on hinged bearings and vertical and horizontal movement are taken care of as is linear expansion.

If you had a walkway running between the buildings as a center spine then you would have more beams and maybe eliminate any purine to get that clear glass bottom so desired.