Floor plan of a single-family house, feedback

Sorry, but how can you generalize from "your" building authority to others? One takes 3 months, the other 3 years. One has office hours, the other does not. One is picky, the other tolerant. One requires building additions, the other does not. Basically: building like application like approval. Especially concerning the facade, i.e. external appearance. And then the construction company: some are very precise and won't just rebuild your subsequent changes easily. The client shifts responsibility to the company in case of trouble, so why should the responsible parties take a risk and build arbitrary, non-authorized changes by the building authority?

Basically: Check the building regulations of your federal state. And possibly ask the responsible building authority. If I look at the building regulations of our federal state, it says that windows, doors and non-load-bearing interior walls are exempt from approval. Accordingly, you can of course change them at any time during the approval and construction process.

If I look at the building regulations of our federal state, it says that windows, doors, and non-load-bearing interior walls do not require approval. Accordingly, you can of course change them at any time during the approval and construction process.

The regulations for renovations cannot simply be applied to ongoing new construction projects!

The regulations for modifications cannot simply be applied to ongoing new construction projects on textures!

Why not? And from which legal basis do you derive that? This was exactly how it was justified to us by the building authority back then. Otherwise, it would not make sense in my view either, because theoretically you could carry out a corresponding modification one day after the completion of the building.

From my point of view, it wouldn’t make sense otherwise, because theoretically you could carry out the corresponding conversion 1 day after completion of the construction.

The time between the building permit and the completion notification is neither "after completion," nor would it be a legal void.

Why not? And on what legal basis do you derive that? That’s exactly how it was explained to us by the building authority back then.

Many building authorities think in terms of procedural economy ("lean, citizen-friendly administration") and apply regulations in accordance with common sense. The legal basis for simplifications is usually simple decrees.

The time between the building permit and the building completion notification is neither "after completion," nor is it a legal vacuum.

That is correct. But why should something be prohibited during that time which would be allowed one day later? But regardless, the most sensible thing is to inquire at the responsible building authority.

This is a general homeowner problem, that the family’s self-image is a still image and "pantha rhei" is overlooked. Not only "children grow up," more attitudes and needs change than one is aware of.

By now, you can arrange stuff in the rooms quite flexibly, among other things thanks to input from some people here.

Besides the floor plan, I plan my electrical stuff, and I make it as flexible as possible. Network socket in the guest room – like, only one? I generally provide at least 2 double sockets. Likewise, most sockets/switches ("sensory," in KNX rather) are designed so that more than one installation can fit in the room.
Only things like presence detectors make it a bit harder—they should be set quite precisely to the current furniture situation so that their detection works as desired—but here you can provide enough "blind" cables from the KNX bus to move them elsewhere later.

The dumb standing wall between the living and dining area is a Feng Shui fail both from the terrace and the living room door perspective, whose "meaning" at least is not clear to me. It isn’t coordinated with anything there, even the symbolic color change in the floor plan is off.

The "dumb standing wall" is a feature that is very much preferred here. I already wrote that the living room door is wrong. But luckily, only we have to like the wall.