We have now decided to roughly replan.
That sounds good, and the plans shown are at least interesting, ...
For the ground floor we have chosen a new floor plan that is a bit less wasteful of space.
... although I wonder why "chosen"? - a house does not become cheaper just by taking one of the floors from a catalog design; "Hang" is actually always a strong hint towards custom planning.
I was now considering taking a roof pitch of 45 degrees with a knee wall of 30-50cm.
Such a small knee wall pleases the vacuum cleaner operator, but doesn't achieve much more. In my opinion, a knee wall that does not fully substitute a dwarf wall misses an essential part of its purpose.