Late to the discussion. Remodeled a tiny little bathroom -- the only one in my 1928 house -- with the same configuration as yours. It was a struggle to come up with a reasonable design. In the end, I tore out the tub, a built-in cabinet and a hall linen closet. Added a shower that is small by today's standards; included a very small bench, which I recommend. I added a floor-to-ceiling corner cabinet between the shower and the window -- it's not very practical but it at least provides some storage. I installed a small, narrow vanity with a sink that extends over the edge of the vanity. The countertop cantilevers over the toilet, providing a much needed horizontal surface. Finally, I had the doorway widened from 21" to 28" (it's all we could do).
Because every single thing was custom, it was very expensive -- $25k for a tiny room with mid-grade finishes in a mid-priced market -- and that was four years ago. Only one person at a time could work in the space, the shower pan was an odd size so built by hand, the shower doors were custom designed to fit the custom shower space, etc.
It's not my dream bathroom; I really miss my old linen closet. But now a tall person no longer has to sit sideways on the toilet and a large person does not have to shimmy to enter the room. There's a space to set down a toothbrush, I can bend over to take off my clothes and I don't have to risk a hip fracture climbing in and out of a bathtub. What I learned in the process is 1) in a small space every inch counts, 2) focus on function, and 3) never ever put white hex tile with white grout on a bathroom floor.
Good luck with your project.
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medicine cabinet and niche below 4" deep
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