Floor plan single-family house, 3 children's rooms, goal: save sqm

I also like the floor plan, so I understand that you are attached to it; but if it is not financially feasible as is, that doesn't help much.

If you stick with the design: place doors so that there is at least enough space behind them for a bookshelf (40 cm, or Ikea shelves are often already 40, so 45) or wardrobes & kitchen cabinets, then 65 cm.

Cancel the stupid open space, it is pointless or just disrupts the organization of the upper floor.

Thank you for your note

Yes, the open space will be removed
It is stylish but simply expensive

... no, it's not even stylish; it's too small for that.

So, a new start with a few components that were good in the old plan. Do I understand that correctly?

Sort of. New start with good old components adopted into the specifications and new suggestions, open to similarities with the discussed design, but without using it as a basis. Good things from the discussed design may only be adopted into the specifications, not directly into the new drawing!
A house plan is like a yogurt culture; you shouldn’t take a seed from a moldy batch for the new one.

well, I don't see it that critically. Against mud, water and snow, you can install a doormat outside the front door. Inside then a normal doormat. It actually works perfectly, even now that we still have gravel outside.

With the right tread and slush, the mat doesn't help, even with heavy stamping. Shoes belong in the entrance area in my opinion.

.. Slushy snow? With us, not even a week a year anymore...

But you can always hope that there will be proper winters again.

I actually find the floor plan pretty good.

You could save a lot of space with the 2nd hallway upstairs. I marked it in purple. You could basically cut out that part.
That means for the upper floor:
- the air space needs a floor to have access to the bathroom
- the storage room and utility room would have to be combined so that only one door is needed from the gallery
- the bedroom would then be very small; that’s why I would then take a few square meters from the office
Otherwise, you can rearrange things differently there, e.g., swap the utility room/storage room with the bathroom because it’s more accessible.

For the basement that means:
- the office must go
- the toilet moves to the other side (at the same time you also have a bigger entrance area)
- the pantry becomes a bit smaller
- the living room too — but I think that doesn’t matter much because of the open plan to the dining room.

But the house itself is pretty cool!