Is it possible to reduce the size of the house after the financing is completed?

A very nice, individual design - thanks for sharing! Unfortunately, I didn’t quite understand the cardinal direction... is the terrace facing west?

By the way, I don’t think the design loses anything by shortening the house. On the contrary: in the longer design, I find the hobby/guest room disturbing, as it pushes the elongated shape of the interior to the extreme and also restricts the view outside (OK, there is only a country road). If giving up this room is that easy for you, I wouldn’t include it in either version.
Is there really anything speaking against putting the kitchen in this corner and the living room where the kitchen is currently? I would find that more coherent, and the water pipes/drains would also line up. The fireplace could then be placed like a room divider or similar between the hallway and the (new) living room. Although I view a fireplace critically in new, highly insulated houses, especially since the distance here could only be very small.
By the way, I would rather see a window seat in the living room, where it can then serve as a second sofa, play corner, etc. For the window seat, we just had a fixed glazing with a 45 cm sill height made. In front of it, a wooden bench runs beneath the window (basically a 60 cm deep windowsill) – done. Please make sure to use special glass (I think it’s called “thermally pre-stressed”), otherwise it may crack in sunlight.
By the way, the sauna is really tiny and I wouldn’t bet that it works like that (at the very least it will be expensive as a custom job). Either you rearrange the bathroom or – even better – plan for a sauna (with an Alpine view!!!) in “Stage 1”. You would only have to run a few pipes and drains (shower, WC) upwards and use the correct screed right away. If you give the room a window on the gable side, you can also convert it any time into a guest room, wellness room, gym, etc. The additional costs for the preparations should certainly be low.

A very nice, individual design

You saw the 7 m (hose) corridor on the upper floor? :rolleyes:

Also, thanks for the feedback and the tip about the window! I thought there would be an immediate wave of outrage about the offset gable. We also had to get used to it at first, but by now we like it because it gives us the headroom exactly where we need it in the attic. The terrace is located in the west with a slight northern tilt. According to the simulation, we would have sun from 2 p.m. until sunset in the summer. The corner of the house at the bottom right points exactly south. We had the idea with the kitchen as well, especially since it would now be right next to the stairs which we could then use as a small pantry. However, the architect advised us against it so far, because otherwise a walkthrough room would be created in the living room, making it uncomfortable. One has to say that the view from the window facing south goes exactly onto an intersection of the settlement road. Not exactly a highlight. I imagine it’s nicer to look into my garden while cooking; besides, it’s also super practical in summer due to the proximity to the terrace. Because of the view issue, the seating window is also on the west side. The sauna currently has space planned for 1.2 x 2.2 m. It is intentionally meant to be only a small model (energy consumption and heating time). I hope we can find something there, but the selection is certainly not that big, you’re right about that. Our architect says the joinery could also build it for us if we want. Moving the sauna upstairs is definitely worth considering. However, that would again limit our possibilities up there, and if I constantly see the sauna while working, that doesn’t exactly boost work morale :p. We thought it was clever to have it right next to the shower. We’ll think about it some more. I’m also playing with the idea of installing a few climbing holds under the slope. The "long corridor" on the upper floor is certainly a valid point, but it can hardly be changed. We want to compensate for that with large windows in the stairwell and an open staircase to the attic. Perhaps the children's toilet will also be removed and replaced by a nice reading nook or something to make it airier. It was basically only added because the space was "left over".

I would reconsider the sauna. 1.20m is very little for a bench plus a comfortable footrest plus space underneath for the infusion. Waving is also not possible. At most, only one person can lie down, with more than 2 people, no one can lie down at all. We will set up a cabin or barrel for the sauna in the garden. There are also relatively affordable kits for this, and you can cool down outside right afterwards. In your design, you would first have to walk dripping with sweat through the whole house.