I have an almost 400sq ft master bedroom including master bath in a two bedroom, 1500 sq ft house. I have a three person jetted tub, a five foot shower with seat, a 55" single vanity. and a separate wc. It's big enough so I can have my dresser in the bathroom containing my underwear/basic wear. So when I wake up in the morning, I can go take my shower, get out of the shower, dry off and put on my basics. Turn around, blow dry my hair, put on my make up. All without ever having to turn on a light in the bedroom and without disturbing my husband who probably is still asleep. I spend at least 25 minutes every morning in my bathroom. One of my must haves during the design was ample space for my hair dryer, brushes and straightener. I want to be able to dry my hair while having my straightener turned on and heating up and I need a dedicated spot for that. At night, my 3 year old can comfortable splash in the tub, recreating a scene from godzilla with dinosaurs and boats while I relax in my recliner and whatch tv, while also keeping an eye on the kiddo because I do not have a door to my bathroom. After the kiddo is in bed, if I want to I can take a nice long soak while watching House Hunters. My master bath is massive in relation to the size of my house, but you know what? So what. It's not "fantasy living". I don't have to live with a child bothering me or knocking on the door, I'm not wasting any space. I spend a lot of time in my bathroom and I enjoy every minute of it. I'm not wasting any space. I don't have marble tile, I have soft, non slip luxury vinyl plank. I have a regular, plain old shower instead of a custom tiled shower. We only have one child. We don't entertain. We don't have a million overnight guests. If I had build 3 bedrooms, I would have one completely empty room that would never get used for anything except maybe some boxes. I don't even have furniture for a third bedroom. But the resale value!!! Who cares? I am not selling. Instead I built a massively oversize bedroom for the one child. If he wants sleepovers, he'll have plenty of room for all of his friends without having to break out an air mattress in the living room. And he can keep all of his toys in his room. I hate toys in the living room. Everyone advised us on this kid friendly feature and that kid friendly feature. Uhm...he's only 3 for one year of his life. So no. I'm not going with a Mickey Mouse light fixture and miniature urinal, things that were recommended to us in all seriousness during our build. Moral of the story. Make your bathroom any damn size you want. It's your bathroom.

IMO, the master bathroom is too small. 30" for a toilet (the minimum allowed) and 30" a vanity is tight even for a guest bath. Your closet is huge proportionally. I would take at least 2 feet from the closet to add to the toilet and vanity space (48" vanity and a 36" space for the toilet) because I would much rather be cramped in a closet than feel cramped in the bathroom. You could also take a few inches from the shower. 5' 34" showers are very common and plenty of room if you are not a large person.

How about... Widen shower to 36-40" wide, filling floor up is no problem... Toilet to rotated so backed up to wall between shower and this new WC, and this slides into the current mirrored vanity space...this is walled into a WC with a (louvred) pocket door that slides toward the shower, allowing the light/fan switch to be on the wall to the right when you slide the door open... The space beyond the WC, into the corner above the current sink is a linen/storage/vanity supply closet...or a small seated level vanity with storage and a mirror for the young lady... 180 degrees from this is the vanity with sink, taking up the upper half of the mirrored slider closet... The remainder of the mirrored slider closet becomes a hanging closet or storage closet accessed from the bedroom directly... The main closet gains about a foot into the current walkway and moves the doorway onto the bedroom wall, mirroring the other door across the entry to the bathroom (into the remaining part of the old mirrored slider). The only real plumbing change is the toilet moving, and the sink moving is as easy as taking the current back into the wall (we hope) and around inside the new wall to rotate the position of the sink.

I am 75 and can still quite easily climb stairs but your issue needs to have you post a to scale floor plan and this was a pretty typical 70s idea and besrt redone to make a nice bathroom space so I would not spend a lot on any 1/2 way work so put the door that you have with a bit of trim to fit and save until you can bring this into this century