Single-family house ~130sqm: balancing rooms

So dear ones, since the topic of building partners is slowly approaching the home stretch for us, I thought we’d start optimizing the floor plan a bit. Even though it was originally only intended as a basis for an offer, we actually like it quite a bit. There are two versions of the house, the downstairs is the same both times, upstairs there is one half-story and one full story. Since I am not a fan of sloping roofs, the price difference is still manageable, and the flexibility in the full story is greater, we are currently leaning towards building the design with the full story. (Half-story design can be seen in the other thread)

Something suboptimal about the designs is that the rooms upstairs are relatively large compared to the rooms downstairs, specifically the children’s room is half as big as the all-purpose room and the bedroom is also very large. Even though the all-purpose room itself should fit (I have seen one with almost the same dimensions at my cousin’s), this is of course not an ideal ratio. Therefore, we will definitely have the wall between the living room and office made of drywall so that it can be removed with little effort if necessary (or if the office is no longer needed).
A suggestion was already made in the other thread to also move the second office upstairs. I tried to draw that a bit (various drafts with pencil, attached is one drawn on the computer), but none of the designs really turn out cool. The rooms not only become very small (~10 sqm) but also get very awkward layouts. I think the upper floor is simply a bit too small for that.

I have also attached a picture of our rough site plan. The location of the garage is almost automatic with our driveway, we would then move the house half behind it into the northeast corner to leave as much free space as possible to the south and west. The 3 plots west of our property are actually one large contiguous plot, so it is very open to the west.

Development Plan/Restrictions
Plot 17 in the plan
Plot size: 700 sqm
Slope: no (max 50cm across the whole plot)
Floor area ratio: 0.4
Floor space index -
Building window, building line, and boundary: entire plot taking boundary construction into account
Number of parking spaces: 2
Number of floors: max 2
Roof type: gable roof, hipped roof, half-hipped roof 30-45°, shed roof 8-20°
Maximum heights/limits: building height = 6m eaves height (no problem)

Client Requirements
Style, roof shape, building type: gable roof, style “normal house”
Basement, floors: no basement due to high cost risk from potential arsenic contamination, instead large attic and technical room in the annex. 1.5-2 floors
Number of people, age: 3 people, he 33, she 41, child arriving in about 4 weeks, no further planned at present
Room requirements on ground floor, upper floor: downstairs living and working, upstairs sleeping and children’s room
Office: 2 offices, he works from home 3-4 days a week, she works as a teacher also often from home
Overnight guests per year: mainly on occasions like birthdays as there is little space
Open or closed architecture: somewhat open
Conservative or modern construction: not old-fashioned but not forcibly modern either. Just a normal house ;)
Open kitchen, kitchen island: yes, but the cooktop may also be against the wall
Number of dining seats: max 4 in normal use, space for extended table when guests are present
Fireplace: no
Music/stereo wall: no
Balcony, roof terrace: no, large garden
Garage, carport: currently leaning toward prefabricated garage with attached carport (she does not like garages). Separate from the house so the driveway remains nice and short
Utility garden, greenhouse: a few small beds, otherwise simple lawn. Much of the garden should be kept contiguous so that it still feels like a garden and not just distance strips
Other wishes/special features/daily routine, also reasons why this or that should or should not be:
second bathroom on the ground floor
A trailer 2x6.5m must also be able to be parked on the property.

House Design
Who is the plan from:
independent engineer who works with the general contractor
What particularly pleases? Why?
Lots of large windows. Office can be shaded around the corner without sitting in the dark. Bathroom without bathtub (please no 15-page discussion about that again)
What does not please? Why?
Children’s room and bedroom are relatively large compared to the all-purpose room, while the second office/guest room is a bit tight
Price estimate according to architect/planner:
Offer from the general contractor for approx. €410,000 turnkey including floors, painting, photovoltaics and most ancillary building costs, excluding kitchen
Personal price limit for the house, incl. equipment: around the offer price, so redesign should be cost-neutral.
Preferred heating technology: ground-source heat pump with underfloor heating

If you have to give up, which details/extensions
-can you give up:
Walk-in closet seems dispensable to us. If we do not change the walls, a thought was perhaps to make it accessible from the bathroom and build in a sauna
-can you not give up:
sufficient storage space in the attic

What is the deal with the guest bathroom? There is no space there to dry off properly. The niche (hallway) is counterproductive. Have you ever considered leaving out the wall between the stairs and the bathroom? There is a lack of accessible and dry storage space.

However, I do find the large rooms on the upper floor quite good. At least you have space there. If you redesign it as in the first picture, you will have to rotate the bedroom by 90 degrees and you can forget about the walk-in closet. Regarding the ground floor: Why don't you recess the door of the WC as has already suggested? I think that's better too.

I also think that it all really fits together. The 11-12m2 offices are definitely large enough. On the ground floor, I would also remove this niche in front of the WC and prefer a real glass cabin instead of the solid bathtub. Then the WC is also reasonably usable. I would remove the wall + door from the storage to the heating room; it only takes up space and you have to close the first door every time to get to the heating.

Did you initially forget the heating, or why is it installed?

Thanks in advance for the suggestions. Tomorrow we have another appointment with the engineer, so I'll bring it up then.

I actually liked the niche in the bathroom downstairs because you don't have to clean the shower cabin as much ;)
But if I think about it again, it probably makes sense to move the door forward and install the cabin there.

The wall between the living room and the hallway is marked as 24 cm, so it's load-bearing. You would definitely have to work with columns to make sure the statics are correct. I'm also not entirely sure how much space you really gain from it. Of course, you could then place the sofa against the columns and basically look outside. Although that also works with a wall. By the way, the door between the living room and the hallway is still on the chopping block; we see little point in using up space for a door and access area when there's another door 2.5 m next to it.

The wall between the heating room and storage room is also marked as 17 cm, so it's load-bearing. One option would be to replace the door with a simple arch.

There is a lack of accessible and dry storage space.

Storage for what kind of items? There is the storage room for noodles, drinks, etc., the vacuum cleaner can be placed either in that room or in the heating room. Since the buffer storage tank is gone, there should actually be some space. Things that are rarely needed can be stored in the attic. At approximately 32° DN, it is relatively large. And then there is also the garden shed for some items.

Did you initially forget the heating, or why is it attached?

As a simple alternative to the basement, which doesn't take up space inside the house itself. I think it nicely closes off the house towards the driveway.