universal design [here: bathroom/tub] for elisabeth: does it have to be one of them ridiculously over-prized systems, whose prizes refer exclusively to the max the health insurances are willing to pay when it comes to de-barrierifying sanitary units?
positively not!
we developed an a) easy fittable/customizable, b) low impact, c) low cost strategy, lending the easy-to-shape eps/xps topped with fiber-re-inforced resin strategy from the surfboard-industry, its surface analoguely waxed for perfect grip.
we added a spray-protecting translucent sheet of plastic held by a bend stainless tube that additionaly serves for holding-on purposes without looking too much like we are in serious geriatry here. it can hold towels too.
the, now exposed, lower part of the wall formerly covered by the bathtub is waterprotected with the means of flat-roof-construction: roofing membrane pressed to the prefabricated shower-unit and just pressed to the wall when on site.
job done in a day.

[not build due to non-approval by the landlord]

or we try the simple, but smart version: