Pinned for the idea. Not sure how much I like the extension over the toilet. If were to do, vanity top should be one piece, with no cut line. Also: Consider how much the extra counter space would be needed.
Kwik Sew 3900 from Kwik Sew patterns is a Olivia& Organizers sewing pattern. A couple of curtain poles, pouchees made from fabric or yarn could then be made to shapes perfectly suited for the items being stored!