Floor plan optimization city villa + fill consideration

Above all, that the shower can be retrofitted easily. Is it always possible to retrofit it, or do we have to say during planning because of the connections that it has to be prepared so that it can be retrofitted later?

I think it is possible to convert it later. How difficult or easy that is, you have to figure out with your architect. It would certainly make sense to place the sink now where the shower is and later remove it from there, move the wall, and instead install the shower. However, with special requests for level-floor or similar, you really need to talk to a professional.

Because of the stair width: Maybe he left it that wide so that the storage room under the stairs doesn’t become too small?

There are stairlifts after all!
I never understand why many builders plan to live only on the ground floor in old age, which anyway has to be remodeled first. When the time comes that I absolutely cannot climb the stairs anymore, what use is the house to me then? At least that's how I see it...

Can stairlifts be installed in any house, or do we already have to consider something regarding the current stair selection/width?

I would have the kitchen window start directly at countertop height. How high are your ceilings?

Best regards
Sabine

Ground floor 2.55 m
Upper floor 2.50 m

From when is countertop height? What do you think of this basil window? Is it old-fashioned?
We have thought about choosing a door window instead of a basil window. We only want to place tall kitchen cabinets on the back kitchen wall and then a large kitchen island in front of them. Then you could make a door window on the right between the tall cabinets and the kitchen island instead of the current window.
I just don’t know how sensible that is, since then we would be set on one kitchen layout forever. An L-shape wouldn’t be possible in 20 years if there is a door window there. Maybe kitchen islands won’t be in fashion anymore. I also don’t want to limit myself.

Stairlift - electricity, stable wall, no spiral staircase, width depends on (stairs or walker/wheelchair), turning space at the staircase landing

Why is the bathroom downstairs not suitable? You can no longer walk stairs - unsteady on your feet, walking aid, probably still nursing service because getting dressed also no longer works well. You are not the agile 65-year-old, for at least one of you it is borderline to still be cared for at home. You don’t take that step before.

At Aldi and similar stores there are shower stools for little money. - But you are no longer steady on your feet, somewhat insecure and then there is the slippery floor.
Grab bar - shower too narrow
Walker - no turning space, you have to awkwardly walk backwards into the shower
Medical wheelchair (already practical, you sit on it while dry, get pushed in, shower calmly, get pushed out or roll, stand on the dry floor - no risk of slipping)
Toilet - where to mount grab bars to help standing up, with walker it gets very tight again, help becomes even more difficult
Brushing teeth, washing etc., all standing up. No space for a seat. Certainly no nursing service.
Rheumatism aches, a soothing bath is not possible, the tub is upstairs. (For which there are lifts, sometimes even covered by health insurance)

Google barrier-free or zero barrier. There you will find bathroom layouts, turning circles, dimensions, etc. It reads well, then I will move to the ground floor when I am older but ...
everything is different.

Try pulling the planned wall into your living room. Then set up the bedroom and measure the distances and compare with the zero barrier dimensions.

Our house is built wheelchair-accessible. Not as perfect as a wheelchair user would plan now, but so that it works well. So far only one appraiser has noticed it. The plan is that we can still use both floors.

What do you say about swapping the kitchen and living room? How would you do it? Then I would completely do without a window where the kitchen is now, and the sofa would be against the wall and the TV against the wall. That's probably the best sofa solution. But then the entrance to the living room would always be through the door between the kitchen and dining room, and you would always have to walk through the dining room to get to the living room. Isn't that disadvantageous? If you were to swap, you wouldn't have a window next to the kitchen because the garage is next to it. You only have the patio doors to the garden. But if you have the sink and cooktop on the island with a cooking view outside, the light should be enough, right? Can you maybe draw something? But the current width of 4.05 meters is a bit too little for watching TV, isn't it?