I personally don’t think the idea of putting the washing machine and dryer in the bathroom is actually that bad, as long as the washing times don’t collide with bathroom usage times. I don’t want to shower, bathe, or get ready with a running washing machine in the background. It would bother me less during small or big bathroom breaks. However, the appliances should be in a cabinet so you don’t always look directly at them. Similarly, you should make sure that there are no piles of laundry or a battery of laundry baskets lying around in the bathroom.
I also find T-solutions very stylish and, compared to the classic elongated bathrooms of the past, something different. Unfortunately, these things are often impractical because they reduce transfer space and also make the bathroom darker. Especially toilets are often real crypts. I have never timed it, but I probably spend significantly more time on the toilet than in the shower or bathtub. I don’t want to spend that time on 1m² staring at a wall. Whether you see the toilet or not is totally irrelevant to me. It shouldn’t be the centerpiece of the room, but otherwise it’s just there and used. Usually, you are alone in the bathroom when using it anyway, and if not, a privacy screen doesn’t help unless there is also sound and odor protection—or do you feel comfortable in a crowded rest stop toilet just because the stalls are nicely opaque???
Now, I have complained a lot, but unfortunately have no really good idea for the bathroom. If the toilet should/must stay at the wall, I unfortunately don’t find a better position for the shower either. At most to the right of the door, where the cabinet is now. That would create a nice corner behind it for things you don’t want directly in view (washing area, but possibly also the toilet), but would make the entrance area extremely narrow. I would always place the washbasin very close to the door because you always go there, and that before leaving the room. So it is quite well positioned. So, if the toilet and washbasin roughly stay where they are and you don’t necessarily want to put the washing machine under the window, there aren’t many options left for the bathtub, even though I find it absolutely unhappy in its current place.
I also somewhat agree with 77.willo. If you want to accommodate "only" the 4 standard trades in the bathroom and it’s not really supposed/can be a wellness oasis, why then 18m²? Heating costs are not so much an issue with today’s houses, but it is wasted or at least expensively purchased space without added value. You can reduce the depth by one meter without functional loss.
Just see if you can really create a small utility room upstairs and reduce the bathroom by a few square meters. With the 4th wall, a better bathroom layout would also be possible again.