Forward-looking floor plan design upper floor

The draftsman truly did a good job. I honestly can't see what is crazy about it.

Well, you are (again) right ;)
A draftsman only draws, an architect provides his knowledge and his studies.
However, I was talking about an architect, who at least had to contribute his stamp.
... crazy, because I see a 2D planning in the initial stage, completely unbalanced. I consider the staircase implementation not worthwhile, so that one can later say: it was worth it – whether in terms of the house or renting it out. The design now has flaws (because the planner doesn't care about many things or didn’t even think about them). Later one has little comfort. And why should anyone rent 140 sqm with a 5 sqm shower bathroom later?
And yes, you have the feeling that everything has to be planned mainly against a boring social environment (even if they can discuss loudly) – I have to smile because we plan so many galleries here, also fully glazed, central stairs etc., and you duly note your “ideas” here, but in my opinion they are only amateurishly implemented.
And that is why I find it crazy that an architect agreed to this. But why should he care, he won't have to supervise the renovation or present himself with this planning.
It's a shame that no discussion took place.

I think it’s good that you are thinking about [in 20 years]. We have done that too and I find it a great relief to at least have the option to rent out parts of the upper floor. Friends of ours also planned it that way. In general, the conversion should not be too complicated and the change of stairs sounds complicated and expensive. Is there not a simpler way here? Stairs outside or a shared entrance after all. Important and not to be underestimated is also soundproofing and, if necessary, electricity.