I would go with the flush variant. But that is just a matter of taste. Under no circumstances a frame around the bathtub.
If it is supposed to be flush, then the only option is that the wall is only 80 cm long. However, then the toilet can be seen a bit
I have attached a photo of a storage compartment to show what I mean. Of course, not in that dimension.
But that only works in the drywall between the bathtub and the toilet. On the long side (to the exterior wall) it won't work.
I think I would lean more in this direction:
Thanks for the idea. Unfortunately, both windows in the bathroom are floor-to-ceiling. In front of the bathroom is the hallway with an equally floor-to-ceiling window.
Although I would really consider whether the shelf opposite the sink should also be removed.
Those are tall cabinets, which we need for storage space.