Need more information...........what is the height variation or fall from the elevation at the top of the stair and where the run would end at the lower landing? What is the length of the run in a horizontal measurement? These are all factors in the code compliant design of the stairs.......not just the width.

In the layout below, I took the liberty to move to vanity and toilet so you don't enter right into the toilet. I am not sure if you have room for that since I can't see the measurements of the width of your bathroom. This is something you can discuss with your architect. The main idea of the layout below is to block the original entrance of the closet so you can have a bedroom door. The entrance to the closet/bathroom can be where your dresser is and move your dresser closer to the window. You would have a choice of a door that swings inward, outward or a pocket door. Personally, I would go with a pocket door so the bathroom would feel more spacious.

More information is needed: How will it be used? What is the view and where? Who will be using it? How many people? Pets? What is your preference of materials? A truly good design address all these issues and more in the programming aspect of the design process. Although hiring a local professional would be great, you can certainly work with a designer via emails, Skype, etc. Good luck.

I suggest you follow the step-by-step guide for creating storage cabinets under the bathroom sink. Take proper measurements - Measure the available available space in height, width and height. Cut Plywood to size - With a circular saw and framing square, cut all the required pieces out. You can use a sliding compound saw as an alternative. Attach the base and sides - Start assembling the sink cabinets by placing the bottom piece of plywood sheet on a flat surface. Attach the back and top boards - Place the plywood sheet for the top part of the cabinet and attach wood screws to connect it to both the sides. Turn the back faces of the cabinet upwards. Keep the back piece over the structure and fix it into place with wood screws. Attach shelves - Place the cabinet in an upright position to install the shelves. Slide a shelf into the structure so it is flush against the back. Attach door - Keep both hinges of the door on the same side of the plywood sheet. Drill them using wood screws into place. Now keep the door over the cabinet structure, extend the hinges to one of the side panels and fix them to make them secure. Fix a hasp closure on the other side of the door, placing it in the center of the hinges.