Basement bathroom door for cleaning supplies. Kitchen to basement door for pantry items. Back of girls' door for barbies. Inside girls' closet for shoes. Inside my closet door for belts and scarves. Entry door for shoes, mittens, etc.
We wouldn't need the second floor, though. Have a basement for storage and keep furnace and water heater down there, then combine main floor utility room with bathroom for larger, combined bath/laundry.