Your pool can be whatever width you want and the upper storeys need not be die die beyond the pool width.
If your pool is until 3m from the boundary, your upper storeys still can be 2m from the boundary. The PE just need to design the 2nd storey beams to be cantilevered out and problem solved.
a building no need to have columns die die at each corner as long as the beams can be counter balanced or pulled back in some way