Unequal width in the planned semi-detached house

Although the OP clearly says that the basement is non-negotiable because they want to have the space. [ < ] If you pull it out of the ground by one meter, you can give it wonderful windows and thus have fully functional rooms. Without expensive and vulnerable skylights and without annoying sloping roofs. Space for a utility room, technology, office, workshop for people who want to work year-round, hobby room, and even children's rooms.

That the OP is willing (and regardless of the cost, even if it costs the house) to put everything on the card "Pyrrhic Victory Headfirst-Through-the-Wall-Basement" we have already understood. A basement under a raised ground floor is objectively ruled out here simply because the profile line acts as a limiting factor – you would have to save this height meter again to that point (whether the minimum permitted room heights would be sufficient for this, I dare to doubt). We still do not know the development plan, but the younger they are, the more often it states that the top edge of the finished floor of the ground floor is limited to a maximum of half a meter above street level). At heart, I could have still agreed with your proposal, but who does it benefit.

The basement is important to us, and we are trying to find sensible options for it.

So you are looking for reasons or a use so that you can justify the basement as "I absolutely need it"? Especially in the context of a semi-detached house, there are not many options. Utility basement. Storage space. Expensive storage. And if you then also consider your budget expectations, it becomes all the more absurd. If I have little money (which is relative in house building, since half a million is not necessarily a lot), then I look for sensible ways to use it. A basement ranks far at the bottom of the list of sensible cost items.

The cellar is simply important to us, and we try to find meaningful possibilities for it.

So you are looking for reasons or a use to justify the cellar as "I absolutely need it"?

Oops, I completely overlooked that the possible uses for the non-negotiable cellar still have to be found, meaning a cellar construction purely out of FOMO (or even fears that without a cellar the cellar spirits would necessarily have to roam above ground, and who knows if they would be content with harmless mischief)? I’d like to have that much money too. But I’d probably rather go on a world trip with an audience with the Pope and fun fact: I’m Protestant, don’t even have a daughter, and I’m not interested in men’s boutiques in Wuppertal.