I think you should explore the idea of getting a Pod on the deck. its like a mini granny flat / cabana with toilet and small multi purpose room. You might have the space for this. Your layout looks fine as it is, and if you have a covered pergola, a second toilet in a pod will works well there. I am a bit against adding plumbing and moving walls to your house. First its a mess. lots of putting pipes under the flooring, fixing the flooring again, also ceiling and conrice works, and you end up with smaller bed, tighter layout. Too much sacrifice and not too much to gain.

based on standard sized fixtures there should be enough space for a small corner shower and single vanity with a toilet squeezed into the space next to the shower (which is narrower than ideal for comfortable elbow room) leaving space in the middle to stand and dry yourself or one person to walk behind another... there also needs to be allowance made for the space that will be used by new wall and floor linings so strongly recommend that you research fixtures and collect pamphlets with specifications and consult a plumber before you buy anything but i would prefer a bigger custom sized tiled walk in shower with glass panel and sacrifice a vanity cabinet for a wall hung sink with in wall mirrored wall cabinet and more toilet room for a more spacious feel

You must be very happy with the end result. it's such a big job, well done and enjoy

We have the same layout as you in our 90s spec built home. We have Bunnings type cavity sliders so I imagine ours are about as cheap as you can get. They are awful - they are noisy when they slide so if one of us gets up in the night for the bathroom, we have to open the door in slow motion so as not to wake the other one up! We have them on our other wet rooms through the house and I find them not too bad acoustically but they don't screen anything in the ensuite. I would not recommend them at all. As for whether to have 1 or 2 doors, the only time I close the WIR door is when I am at my wits end haha! It's a great space for a private phone conversation but I really couldn't be bothered closing the door any other time