Union of two plots - redefine the building envelope?

I consider the marked building envelopes to be contestable due to uncertainty - there is no discernible rule according to which they were placed.

Point 1 is at the lowest elevation at 296.3 m. Point 2 is at 298.3 m, the distance between 1 and 2 is 63.6 m. Point 4 has a height of 296.7 m, point 3 is at 297.8. The distance between 3 and 4 is 35.5 m. A slight slope from south to north is therefore present.

That is pretty flat. For paved areas, 2-3% is used, and your property is partly even below that. A basement is really not necessary because of the slope.

I consider the marked building envelopes vulnerable due to vagueness - there is no rule visible according to which they were placed.

A certain rule can already be recognized in the street sequence, it is just not visible in the excerpt. But from a practical point of view, a building envelope in the middle would even fit better visually into the street. The purple X above house number 15 will never be built because half of the plot is covered by the garden pond and used as a garden by house number 15. In our case, it would also be true that only one house will stand on the two building plots and not two, so the pink line and the building envelope in the middle would fit better with the existing houses than if we build set back to the rear ;)

With very high ceilings, intermediate levels could be inserted on a sort of platform. Just Google "FAZ building at height". Although it mostly concerns old buildings, I would also find it appealing in new construction. Although certainly not the cheapest solution

if you build the ground floor with 6 meters or simply

Just thinking neutrally: that would violate something… ultimately no building permit and extremely expensive. Not proportionate at all. Is there a floor area ratio/building coverage ratio?

Is there a floor area ratio/floor space index?

Unfortunately not readable in this box on the map itself, the scan is too poor. But I have only had the development plan as an online version so far and have not yet been directly on site at the municipality, they should have a better quality there ;) There are quite a few numbers in the text... o_O

What do you prefer, an angled bungalow or rather a 1.5-story house with a higher knee wall? Maybe you can even present both options to the building authority and see how flexible they are, and which option has a better chance of approval.

We also have two adjacent parcels, although one is significantly smaller. We also applied for and received an exception from the development plan. However, as the owner of parcel A, I had to approve that my neighbor on parcel B (that is me :) ) deviates from the development plan. With a cooperative building authority, that should actually be possible.