I never understood the floor plans of a narrow, windowless closet in between the bathroom and the bedroom.
However, since we moved to our new house, I suddenly understood the genius of the closet as the sound barrier between the bathroom and the bedroom!
Our current bathroom layout opens right into the bedroom so that if one spouse needs to wake up earlier than the other and get ready for work, the flowing water, hair dryer wakes up the spouse still in bed:
So, instead of just another narrow closet in between the bathroom and bedroom floor plan, I thought I might as well try a redesign with my preferred typical Japanese bathtub + shower layout -- a 'water proofed' room housing both the shower & bath tub side by side so once one's cleanly rinsed via the shower, he can jump right in and soak in the steamy bathtub.
This particular layout tries to retain a similar dimension as the current layout:
We could even insert one of those tiny sinks in the water closet. The flaw with this layout though is the toilet's placement right next to the closet which may seem disconcerting ... This layout also moves the closet sound barrier from the next door bedroom.
In spite of the downside however, note the penetrating skylight in the sound barrier corridor!