What would you build on this property?

In Bavaria, IMO, an attic is a full storey if more than 2/3 of the area is higher than 230cm.

I thought there were no more partial storeys in BY.

There have been no full storeys in the Baybo since 1998, it is now only referred to as storeys, you are right. But: (7) As far as § 20 para. 1 of the Baunutzungsverordnung refers to state law for the definition of a full storey, Art. 2 para. 5 in the version valid until December 31, 2007 shall continue to apply in this respect. And as far as I know, development plans must always be interpreted in accordance with the law applicable at the time of their issuance.

The living area on the upper floor, which has a ceiling height equal to or above 2 meters, may only amount to 2/3 of the living area on the ground floor. (Niedersachsen)
This means with a 4-meter eaves height: approx. 1 meter knee wall with a 45 degree roof pitch (roughly stated).
So it corresponds to your basic idea of a standard gable roof house.

If you want to experiment with a shed/offset shed roof, an architect can help you with that.

Doesn't single-story mean that the attic floor cannot be a full floor?
But I have no idea how it is in Lower Saxony..

I would tend towards a bungalow with a basement (1m out of the ground), with a flat hip roof on top (I assume the author meant a tent roof..).

A hip roof is unfortunately not allowed! For a bungalow with a tent roof, the plot is probably a bit too small if you want 140-160 sqm of living space...

Personally, I like the idea of a stepped floor with a shed roof plus a roof terrace - or are there really no "partial floors" there?

Roof terrace that would probably never be used in the single-family house area...