Well, this does feel kind of strange, but this is my bath/shower room.Sounds rather like a traditional Japanese bathroom, which is what we want.
The Japanese have extremely civilised ideas on modern plumbing. One washes before getting in the bathtub which keeps the water heated while you soak and the toilets have a built in bidet.
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Or this one
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https://www.realestate-tokyo.com/living-in-tokyo/japanese-culture/modern-japanese-bathrooms/
There is a shower curtain that you pull across the doorway and a drain in the middle of the shower section floor for water to flow out.
The entire house floor is one level and made of concrete. Just bomb a bucket of water and bleach on the floor and push it down the drain. Simples.