In the solution that I propose for the apartment of 640 sq ft I chose to consider as entrance the existing door on the east side. In this way you get some advantages. First you can have the bathrooms and bedrooms on the north wall; then the entrance is near the living area minimizing the length of the routes and the surface of hallway; finally, the living area is on the south side, the brightest area of the place.
The kitchen is open onto the living area and it's equipped with a counter-depth refrigerator, the dish washing machine and a peninsula for breakfast.
The bathroom has a cabinet with a stackable washer/dryer unit and a linen closet.
The bedroom has a desk and a large walk-in closet.
All along the north wall there is a 8" wall that allows you to hide the foundation wall and existing pipes.
In the hallway there could be the door which will expand the apartment including an extra bedroom (or office) with attached bathroom, a living/game room and a gym/workout area.