Since you are building with a basement, I would refrain from that and rather build a room there with a light well.
That is currently also my line of thought. However, my experiences from this forum are that attic conversions are generally recognized and accepted, but living space in the basement causes hyperventilation.
Especially because we will have a large basement, GU1 is currently planning to design 2 rooms of it as living space. GU2 will at least (due to the energy saving ordinance) install the pipes for the underfloor heating but will not connect them. What is better for living will probably depend on the seasons. Getting the attic cool in summer will likely be just as difficult as heating the (uninsulated?) basement in winter.
A light well is actually quite suitable on the south side since we have the slope and a lot of light would enter from the south. In addition, nothing useful can be done with the 4m strip towards the southern neighbor in the garden anyway.
In particular, considering stairs to the upper floor ruins many floor plan options on the upper floor. I actually do not want that because of the basement. GU1 practically forces a staircase to the attic on us. GU2 would at least design the rafters in the roof so that a retrofit would be possible.
So something like this? [ATTACH alt="EG mit Seiteneingang.jpg"]41891[/ATTACH] [ATTACH alt="OG mit Seiteneingang.jpg"]41892[/ATTACH]
From my point of view exactly like this!
I am curious what the two GUs will tell us next week. I will keep you updated.