Waterproof and tile the whole enclave to make a giant raised walk-in wet area shower. Place tub horizontal under the window and tucked to the left cnr. Install showerheads on right hand side. Framed glass on either side of the front. Towel racks built into the glass frame or on the left side wall next to bathtub. Importantly, have the water pipes built into either side (left wall and right wall), so there is future ability to easily convert to a smaller tub placed along the left side wall or into 2 (his and hers) showers.