Cherry, I think you misunderstood me. I'm not saying a custom built desk, I'm saying could you swing the desk around so it's not facing the two doors but rather at a right angle to that wall facing outward. The part I had custom made was a screen to hide the cords and my legs. You could improvise that with plants or pretty boxes or whatever. I feel like your room needs to breathe a little bit. It's easy to overlook the possibility of using middle of the room floor space, by lining it all up against the walls. Your view from your desk isn't very pleasant but mayb swinging it out would give you a more open view. My pic may not have been very descriptive. Let me send you another. Would this idea work for you?

first consider any good use of the space from inside the bathroom (you could then fill in the opening from this side for more walls space and/or shallow bookshelves etc and access storage from the bathroom otherwise add some adjustable shelves and a hinged door between the post and the wall and fill in the rest of the space and/or cut panels of painted craftwood that can be screwed over the opening and removed for access ... quicker and cheaper would be a curtain gathered top and bottom to conceal the opening and hide all your stuff

You could add a chaise lounge or a comfy chair and table for a reading nook or an office area if you need one, a computer area but whatever you do don't over clutter it keep it sleek and sexy and or a comfy chair as suggested with a little side table for reading, I also like the idea of a place to put coats, shoes etc if you must enclose it. Maybe even a small wine bar? with a couple of stools. I decided to google is and will give you a link to many pics to give you more choices. https://www.google.com.au/search?q=pics+of+what+to+do+with+space+behind+floating+stairs&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjFy-n9p4vZAhUEF5QKHSvhAOMQ7AkISg&biw=1280&bih=893

Gorgeous! Your clients must be thrilled with the result. I love the brick wall that remains... creates a feature. Great use of space under the stairs! Could pose a problem getting back up them tho after you've enjoyed a few glasses of your favourite shiraz ;)