It looks great! What is the depth of your powder room?

It wasn't measured on the mock plan but i'm guessing its about 6 1/2 feet based on the other room sizes. the walk in closet is 10 deep.

As long as the shelves are no deeper than the toilet tank how could there be any issue besides esthetics?

It will work. You will need at least 5 feet. With your in-swinging door, it will feel tighter than if it were a pocket. Or, you could build it IN to the wall behind the toilet, rather than bumping the toilet xfar from the wall.

I think Brickeye is thinking it would hang above the toilet. But, I think you want it built IN, like your picture.

Building it into the wall instead of pushing the wall out is a great idea.

Another is to change that door to a pocket door so that you will have the illusion of more space.

Your concern is the vent stack in the wall behind the toilet.

Have that wall built with 2x6 or 2x8 instead of 2x4. This would take a couple of inches from the closet but will give you room for the shelves. The area for the shelves would need to be framed the same as a window. You could put 6-8" deep shelves.

Standard rough in for closet flange is 12" to the center. Have your plumber rough it in at 12" + the depth of the shelving unit you intend to have built.