I just bought a house that has an upstairs half story. It was previously set up as 2 bedrooms divided in the middle by a very small bathroom. In fact it just has a toilet and tub in the bathroom and the sink is attached to the outside of a bathroom wall, sitting in one of the bedrooms.
I want to turn the entire area into a master suite. Having never done this I have no idea how easy/expensive it will be to rework the plumbing a little there. I think I can leave the toilet where it is, but the sink and tub plumbing would need to be moved some. The current tub has a handheld shower head because the water is currently coming out of the shorter/slanted side wall. Its an older house (67yrs old), if that changes things.
In my opnion I would first find out where all the plumbing goes throughout the upstairs and then determine the final placement of the utilities. Make sure they are functional for ergonomic use. In other words give each utility enough room for the average person to fit. After you determined that. You can then determine where you plumbing can go. Your house is not that old so replacing the old drain pipes and supply lines are not that difficult. Just make sure you conform with the local building codes. Let me know if this helps. Tom
My apologies from bringing this back from the depths....
Did you have any sketches or pictures of your original setup - with the 2 bedrooms and the bathroom upstairs?
I have a 1.5 storey house with the same setup as yours without a bathroom and I am thinking of putting one upstairs - either utilizing the centre closet, or popping a hole in the wall thru the attic space and making an ensuite off the master.