considering all the other advice here's some more suggestions. ..showers are 1200mm x 800 - 900mm, three handbasins would each be about 700-800mm wide but, custom made with a single top and three small drop in sinks there would be more available counter space, matching mirrored wall cabinets would reflect light from wide, above door height windows on both sides with a solid timber hinged door and security screen (although a sliding door is the neatest and most waterproof privacy would be a problem and frosting the glass more expensive and not very private at night)...the best option will be the one that suits most of the users most of the time but it would be a shame not to have external access and there's plenty of space and so many possibilities

What is the condition of the current bathroom and kitchen? Also what do the estate agents in your area say? ie will an additional bedroom and ensuite add value, or will an extra family room add better value? or will just a cosmetic upgrade be better?

as a fellow downsizer my suggestions are aimed at comfort and easy access.. rotation of the ensuite allows for more walking space and room for a small side table and chair near the bath. the toilet room closer to the bedroom door keeps wet floors away from the vanity and consider adding grab rails for comfort in the shower and they also make great towel rails and easier to add during construction ...I've stolen a little space off the living areas to add extra walking space in the guest room and study, these rooms are now interchangeable (if you prefer the study with a view) and the guest bathroom has external access for the pool...strongly recommend you identify purposes for all the storage areas so spaces can be designed to suit eg the space on the right as you walk in from the garage could be ideal for sit down bench with wall racks for coats etc or a counter for sorting bags of groceries ...you created an excellent plan and I would be happy to change or explain any of my suggestions

if it's a rental i would invest in some tall modular bookshelves eg Ikea billy with combination of open shelves, solid or glass doors and shelves, space for printer and fax on top of matching filing cabinet and a chest of drawers for office supplies and set down counter spaces, wall shelves above the desks for books and reference materials, keep your original mismatched desks and buy some quality desk lamps and extension cords with circuit breakers and cable organisers to make sure you have the necessary power where it's needed.... if it's your own home i'd have the same furniture and invest in some extra power points, a dedicated phone line for fax and internet, and make sure you keep all receipts for your business tax and depreciation expenses...my suggested floor plan has the desks on opposite walls, bookshelves across the end wall and above the desks, twin filing cabinets, wall shelves, space for the aircon and a spare chair for visitors but the precise amount of storage depends on the products and services you supply and what equipment you need