We got the heating solution from a reference house of the builder, and it seems to work there
hm, a wall-mounted boiler?
A gas boiler with 300 liters of domestic hot water doesn't fit there. We have a larger niche, but the plumber really complained that he couldn't reach it with his monkey wrench or whatever. The water pipe was then relocated in our house. Our heating is only in one corner, two sides are free, so you can access it.
The problem with these pre-cut symmetrical Frisian or other third-gabled houses is that everything is predetermined. The kitchen corner and utility room may be okay in terms of size, but the living area is relatively too large compared to everything else. The living room is more than generous, but there is no storage space or PC room.
The basement or shed is not a place where you can just store your sports equipment or wrapping paper.
Even if you see it differently now: your dream house will then be spiced with some clutter corners.
You can also imagine better things than falling asleep next to the rattling printer or a partner who is still using the internet ;)
With 123 sqm, definitely use every sqm. Not the basement, not the shed. Create comfortable space: free space on the upper floor for storage, reduce the bedroom size, the rest as an office (with seasonal wardrobe storage).
I find the children's room size okay for the house size.
And no: 140 sqm is not necessarily oversized; the two of us have 135, okay... it can be smaller, but it doesn't have to be.
I already find 123 borderline, but completely okay if you can't or don't want to live bigger. But then you have to face reality and give up oversized gimmicks or air spaces that belong in big houses.