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.
I'm thinking of something like this for where my stairs are now. When we move the stairs I want to keep the wall with the open view to the living room. I think it would be a great breakfast area for the kids before school