Is it sensible to preserve the basement and build the garden house on top of it?

Hello! We have newly built in the front yard of an older house, which is partially subsided. The older house is from the 60s and partially basemented. Everything that is not basemented has significantly settled. We are now considering whether we should completely or partially demolish the house. We would like to continue using the basement. Is it sensible or even possible to completely demolish the house except for the basement and build something like a garden house on it? Or a partial demolition and leave only the foundations standing on the basement? We would like to put a shed roof with a solar system on it... My questions are, what would you recommend? Is it worth keeping the basement? What would be the cheapest option? Thank you very much in advance.

We have rebuilt in the front yard of an older house, which has partially subsided.

That means the new building already exists, and it actually lacks storage space if the basement is demolished; the demolition was not part of the building permit, ...

We would like to continue using the basement. Is it sensible or even possible to demolish the house completely down to the basement and build something like a garden house on top of it?

Basically, I am positively inclined towards preserving the basement, but there is still a lot of information missing here (and a picture is worth a thousand words). Would have, could have, should have: my "golden" advice would have been to ask this question earlier and to coordinate the ensemble of the new house and the old basement in terms of planning and concept in advance.

I also agree to preserve the basement and, if possible, more of the old house.

As already asks, are there legal requirements that oppose this?

Instead of the solar thermal system, I would recommend photovoltaic.