Legal and technical requirements in bathroom planning?

Hello,
the bathroom renovation on the ground floor is getting out of hand.
By now everything has been gutted and now we are moving on to planning the new pipes, and for that of course we need to know where what is going, and that's where the problem starts. The old man is stubborn with old age, and the plumber is a real expert (seriously, professionally he is really great), but when it comes to customer contact, he is as flexible as an anvil, and I'm stuck in the middle :(
Problem one: radiator with towel rail. The plumber says that doesn't exist, but dad found something like that on the internet. After long inquiries, I found the problem. It's about the plumber having to guarantee a heating output that isn't given if towels are hanging on it—I can even understand that.
Then the old man wants a bidet, "not possible" because the wall is too weak. Are these things really only available as wall-mounted devices?
Then the walk-in shower—does it absolutely have to have a foldable glass wall? Is it no longer allowed to hang a shower curtain?
The old window is "in the way," a plastic window will be installed anyway. The recess will of course be tiled with a proper slope, just as the whole bathroom will be tiled high up anyway.
Am I really imagining this too simply? Or has a bathroom renovation today really become rocket science?

I don't even want to start on the mystery piping of the last 70 years; special problems will come up for me there anyway.

Of course, you are allowed to hang a shower curtain. You can also leave it completely open. That is your decision.

I can hardly imagine the wall being too weak. There are pre-wall installations for that.

And there are towel radiators. They provide sufficient heating performance even with towels hung over them. Especially with a conventional heating system with radiators, that's not a problem. We also had it as the only radiator in the bathroom; it was completely sufficient, it just needs to be large enough in size.

So, should we call in a second expert?

Am I really imagining it too simply? Or has bathroom renovation really turned into rocket science nowadays?

Answer 1: No Answer 2: No Show your plan.

Is the floor plan already done? Can you sketch it in? What is the size of the bathroom and has a heating surface calculation been carried out? Besides a radiator (feel free to have the heating engineer/plumber size it), I would also plan a towel radiator. And if this is only meant to hold the towels without having to turn it on ("having is better than needing"). Wall-mounted ceramics are installed on [Vorwandinstallationen]. The cladding / [Vorwand] is made with gypsum board. Behind the gypsum board are wooden panels – this way you can hang more weight. A walk-in shower can be executed without a "door" depending on the size.

So, should we call in a second expert?

Then it just becomes different....... ;) The "problem" seems to me to be more about the "old man". If it is his apartment, then he should probably arrange it directly and alone with the heating engineer, otherwise you can only lose out. If it is yours, I would forgo a bidet depending on the space; we can’t see from the plan whether you even have a half-wall. Of course, there are also floor-standing ceramic pieces. I don’t like folding walls for various reasons; I’d prefer a clear plastic curtain, which is definitely practical and can be adapted as desired! I generally find towel radiators overrated and here they are senselessly connected to the heating system (gas underfloor heating); zero function. I would rather take a towel rail or similar that can be placed freely. When I shower in the morning, the towel is dry again in the evening, even without a radiator.

Am I really imagining it too simply? Or has bathroom renovation really turned into rocket science today?

No, it is rather often done.