Land division / construction - What is possible?

yes that's true, but I can't imagine that I would want someone living above me in my property.

Due to the unsuccessful conversation with the architect (we were shown a certain lack of interest), we are now considering whether we should inquire elsewhere after all.

What does lack of interest mean in this case? Just because of an unsuccessful conversation, you can still maintain contact. I would follow up with the architect again. Then you just say that 5.5 is too narrow for you and move on.

I cannot imagine that I would want someone living above me in my property.

I remembered ...

The plot will probably belong to my cousin and me.

... and in that respect, it would not be a multi-family house with strangers.

What does disinterest mean in this case? Just because of a failed conversation, you can still maintain contact. I would follow up with the architect again. Then you just say that 5.5 is too narrow for you and move on.

yes, I think that is the appropriate step, otherwise we have to look for another expert. He will probably be able to come up with something, and then I will come back to this and look forward to feedback on the towel bowling alley. Jokes aside, we also see that this whole thing is not done just like that. For us it is an option, but if the floor plan doesn't suit us, then we have to face reality.

if the floor plan doesn't suit us,

But it doesn't even exist yet.