First of all the images you posted you cant make anything out what you got there. Secondly you should contact a local Architect when doing something like this, not only for structural reasons, but window design as well. He will layout window detail based on the window sizes available from a certain manufacturer or you can take his drawings which indicate opening detail to a place who sells windows, and they have catalogs of window combinations and sizes to make it work with what you have.

Our bathroom is the smallest room in our house. Width = 5 feet and depth = 8 feet. This is this the size of our bathroom. What does this size give us ? A step over bathtub with shower, A small vanity with matching small medicine cab, a toilet (of course), shelves over the toilet, a floor to ceiling (skinny width) closet to house things like towels.

Are you speaking of a glass shower enclosure? What is there now? If a shower what size? Please either pictures with dimensions or a floor plan to scale with dimensions.

Are you referring to any specific plan ?