ᐅ Single-family detached house with a full basement

Good evening everyone,

Due to the limited availability of existing properties and some very specific requirements, we are planning a single-family house with a few special features. First of all: I am open to all suggestions and also welcome honest, well-founded criticism.

Some basics:
1. We have two children (3 and 1 years old) and are planning for a third, so there will be five of us eventually.
2. DIY work is almost out of the question. Only painting and laying carpet flooring in the basement are tasks we feel capable of doing ourselves.
3. I definitely need a separate home office since I mostly work from home (planned in the basement, see below).
4. A very large hobby room is a must in the basement. It should be rectangular and at least 2.70m (8.9 ft) high (hence basement ceiling height 2.70m).
5. We want to be as uninvolved as possible in the construction, so we have only looked at prefab house providers so far and would currently prefer a turnkey construction.
6. WE DO NOT HAVE A PLOT YET! Therefore, the house has been designed so that its roof and number of floors should fit many potential plots roof pitch 35 degrees, knee wall 120cm (47 inches).

Today we received an offer from the prefab house company that seemed "quite suitable" to us so far. The salesperson was to consider the following requirements in addition to those mentioned above:
1. The children should live on the upper floor. In addition, a guest room/home office (for my wife) should be included there.
2. The master bedroom should be on the ground floor with its own bathroom. A separate guest toilet should also be on the ground floor.
3. My wife wants an open L-shaped living/dining room if possible.
4. A small separate pantry should be located behind the kitchen.
5. We are not into "frills." Large galleries, huge bathrooms, big hallways, etc. are considered a waste of space and money. So rather functional and practical.

Our initial assessment
Without preempting your professional opinions, we find the following aspects of the proposed floor plan problematic:
1. The biggest concern is the kitchen’s width of only 2.15m (7 ft). This is unacceptable. The seller then suggested extending the kitchen by 1.20m (4 ft) with some kind of "addition" (sorry, I don’t know the correct technical term). However, this extension would cost at least 12,000. We were not very enthusiastic about this idea.
2. The guest/home office on the upper floor also seems impractical for the same reasons.
3. In general, I find the angled room for child 1 on the upper floor not ideal to use.
4. Isn’t the master bathroom too narrow at 1.8m (6 ft)? Of course, we are slim but these dimensions seem tight.
5. I consider both the type and location of the staircase suboptimal. I would prefer it on the side, and we want a continuous staircase from top to bottom, not one that leads down through a separate door as shown in the plan (not a dealbreaker, but feels odd to us, especially given the already narrow kitchen…). What kind of staircase would you choose? Where would you place it?
6. Is the arrangement of the bathrooms acceptable? From a layman’s perspective, I thought that at least the children’s and parents’ bathrooms should be above each other.
7. How do you assess the lighting situation through the windows? We find it suboptimal in some rooms. A bright house is very important to us! Where else would you add windows?
8. Surely subjective as with many things, but how do you evaluate the fact that my office is in the basement? I will be spending a lot of time there.

Thank you very much for every suggestion! I am aware we are still at a very early stage, but our goal is to have a "reliable" floor plan soon that will largely be set (I understand that the layout of rooms will ultimately depend on the specific plot and might require further adjustments).

Questionnaire
Development plan/restrictions
Plot size: not yet available, should be 600–1000m2 (6460–10760 sq ft), having a garden is very important to us!
Slope: n/a, we are generally open to a sloped site (for light in the basement)

Builders’ requirements
Style, roof shape, building type: Open to almost anything... my wife is not a fan of the "cube" style. Planned as roof pitch 35 degrees, knee wall 120cm (47 inches)
Basement, floors: Full basement (mandatory, see above), 2 floors (or does the upper floor not count fully because of the knee wall?)
Number of people, age: 4 people (39, 34, 3, 1 years old), planning a third child in the future
Space requirements on ground floor/upper floor: Ground floor: living/dining room, parents’ bedroom, parents’ bathroom, guest toilet, pantry; Upper floor: 3 children’s rooms, guest room, children’s bathroom; Basement: hobby room, office, utility room
Office: Family use or home office? Main workplace is the office
Guests per year: several times a year, probably more in future due to children
Open or closed architecture: Don’t quite understand this; "open" in living/dining, but no gallery or entrance hall, please!
Conservative or modern design: Either possible
Open kitchen, kitchen island: Definitely. A kitchen island would be nice (not realized in the current design, also not a must-have)
Number of dining seats: 1
Fireplace: Prepared, included in budget with 4,500
Music/stereo system: High-quality integrated stereo system planned in the living room, I will handle this myself
Balcony, roof terrace: Not important because the garden is our priority.
Garage, carport: Secondary for now (budget!), both could be added later and should thus be kept in mind.
Kitchen garden, greenhouse: Garden is very important, especially to my wife. It doesn’t have to be huge, but she wants a kitchen garden and enjoys regularly redesigning it.
Other wishes/special features/daily routine, reasons why or why not: Very large rectangular hobby room with high ceilings.

House design
Who designed the plan: independent sales agent of prefab house company
What do you particularly like? Basically, our wishes (see above) were taken into account. Admittedly, the hobby room is my thing and I quite like it.
What do you not like? See our eight points above, especially the kitchen being so inadequate.
Price estimate according to architect/planner: 415,000 for the entire house (DIN 277 living space ground + upper floor = 177m2 or 1905 sq ft, basement 88m2 or 947 sq ft)
Personal price limit for house, including fittings: 450,000
Preferred heating technology: I have no idea! Planned is a condensing gas boiler with underfloor heating (also in the basement). Suggestions are welcome here as well.

If you had to give up, which details/extensions
- Could you do without: Everything is already planned very functionally in our opinion, so no "frills," no oversized bathrooms, etc. Well, except for the hobby room, I know
- Could you not do without: See above.

What is the most important/basic question about the floor plan in 130 characters
How can the kitchen be designed/integrated properly, staircase better placed, parents’ bathroom improved, and upper floor clarified further?