Floor plan: who has the master bedroom on the ground floor?

We deliberately kept the living room relatively small, as we currently spend very little time there. Our focal point in the current rental house (built in 1960) is the kitchen with dining area/bench, where our daily life takes place.

Then the kitchen/dining area should also be placed at the center in the nicest part of the house, ideally with access to the terrace, and the sofa/TV area rather banished to the darker area.

..whether it should be a "standard floor plan" or rather a standard bungalow with stairs and a shallow roof pitch, so that the desired children's room and a hobby multipurpose room (alternating with a bedroom for fresh parents) can still be accommodated in the attic. The ground floor then autonomous without a basement, which one cannot also frequent 5 times a day for cleaning supplies and drinks.

I had the idea of the bungalow too. However, the plot size with 4xx m² is not generous.

I find the floor plan successful.

We also don't have a window in the kitchen area ourselves, but the room is overall bright enough due to large window surfaces, so it works in the kitchen as well. And for real work, I turn on the light anyway.

We also have the bedroom on the ground floor and sleep very well there.

A truly wheelchair-accessible floor plan is not easy. If it is to meet this requirement, I would personally reread the DIN for it. Especially in the bathroom, I would position the connections from the start in such a way that it works later.

In any case, I would not plan the washing machine in the basement. Falling down the stairs with a full laundry basket is one of the typical household accidents even for people without balance problems. Therefore, I would at least provide the option somewhere on the ground floor to place the washing machine.

However, the plot size of 4xx m² is not generous.

However, with a floor area ratio of 0.4. 160 sqm of floor space should be enough – I don't want to harp on the budget, but if you only look at the wishes or necessities of the OP, I don't see three floors.
What some people wish for here, namely to live on just one level, is practically a given here due to his physical limitations.

Haven't read everything, shame on me. But if the sense of balance and climbing stairs are already in question at the tender age of 33... how secure is the well-paid job then? Will one still be able to perform it reasonably safely for the next 10, 15 years? I don't want to paint a gloomy picture, but a house for a total of about a million is an investment over 30 years. If it is already vaguely visible now that it could lead to occupational disability in 10 years. Especially since then you have to outsource everything, really everything at the house, prospectively. Gardener, etc. Otherwise. Bedroom on the ground floor. One can do that, one can get used to a tiny living room and the children upstairs are happy about huge children's rooms.

I’ll bring another idea into play. I understand that you want to avoid stairs due to physical condition. That is understandable. Now you are trying to pack everything relevant onto one floor and are building a lot of unnecessary space on the upper floor. With a construction price of 3k/m2 and a price of around 40k for a shaftless home elevator, it might be cheaper and better for you to plan with 2 levels and simply install an elevator. You are simply building less enclosed space. The entire floor plan becomes less congested and you can optimally use the 2 floors that are structurally given to you. Those with special requirements should feel free to also afford to think differently. If you’re already moving away from the standard, why not be consistent right away. We have never regretted our unusual house for a second and have deliberately ignored many conventions.