Single-family house floor plan 175 m2 - improvement suggestions?

Thank you very much for your answers!

The living room is intended to be a pure living room (sofa, TV), the dining table should go into the kitchen (by the seating window).

We currently have two children and therefore two large children's rooms; the third small room will initially be a study, but if a third child should come later, it could be repurposed.

For the dressing room, we deliberately planned the door from the hallway so that you can place wardrobes on the left and right. But of course we can also plan a door from the bedroom.

Regarding the hallway, I have also considered initially leaving the door opening as a passage without a door so that more light comes into the interior hallway. Alternatively, the entire wall between the staircase and the interior hallway could be removed (as long as it is occupied as a single-family house) and only later a wall built when it is used as two residential units.

Why do you endure such restrictions for decades just so that you can eventually share the house?

People in old age usually do not want anyone in the house. Additionally, the living unit is not obviously barrier-free (wide doors, bathroom, ...).

Neither fish nor fowl.

Why do you endure such restrictions for decades just so that you can eventually divide the house?

That was also the first question that came to my mind when looking at the floor plan. Why does the house have to be divisible at all costs? Don’t you want to live nicely and comfortably now and create a cozy family home? Who knows what will happen later?! Many years will pass by then, and maybe everything will be done differently and more modern anyway. I have a friend who did it the other way around; she bought an existing two-family house because of her four children and converted it into a single living unit. It is totally uncomfortable, even though the doors in the stairwell are gone and the passages have been widened so that the staircase no longer stands alone, and a large living-dining area was created on the ground floor. Despite everything, you can still tell that it was not designed for one family. And unfortunately, your floor plan has the same impression. If there are no really solid reasons, other than the current idea that you want to downsize in old age, then I would start over from scratch and plan a “proper” single-family house for a family with still small children now. You will get more out of that in the coming years than thinking about old age now.

Neither fish nor flesh.

And for the whole life, only lazy compromises. Not only for you, but also for the children.

As often as the OP emphasized in the opening post that divisibility is important, it is pointless to criticize this point. Without scale-appropriate furnishings, it is difficult for me to assess the floor plan, but I also suspect that it will be particularly difficult on the ground floor. Less hallway is actually not possible, and I find the current one almost too narrow – and too dark.

We actually like the floor plan very much, I just find that way too much living space is wasted on the hallway/vestibule/staircase.

Given the stated wishes, I find the floor plan acceptable. The hallways are not too large. On the contrary, I think the space for the wardrobe and the entrance area as a whole is far too small for 5 people.
Can the square meters be better distributed if one foregoes the later separation and the conservative construction method? Yes, very likely. But that is not desired. Whether one wants to live like that is another question.