Which floor plan to choose for a 145 sqm flat roof? Ideas?

I prefer the first floor plan with the proposed changes. The mini office in draft 2 feels more like a storage room to me, and even if it’s enlarged at the expense of the bathroom, it remains a narrow, uncomfortable cramped room estimated to be about 2.20m(?) wide. Also, it would annoy me to have to constantly do this egg-and-spoon race with the groceries around the endless staircase to the kitchen.

But maybe there are more options? Tell me the maximum square meters and the building window limit! Maybe someone still has something up their sleeve. :)

145sqm-150sqm maximum.
Building envelope is 9x12m.

Only a small bathroom for possibly 3 children? That would not work for me at all. I find your windows too small in the first draft, a floor-to-ceiling window in the guest toilet? We also have a narrow, long window above the bed in the bedroom. That is nice, but there is also a 1.76m wide, floor-to-ceiling window, otherwise it would be very dark. The children's rooms also need enough light, better a bit brighter than too dark.

Best regards
Sabine

Flat roof means no attic; I don't see a basement. The green floor plan has two offices, the upper one actually only suitable as such, the lower one then for a child far away from the other two?

I wouldn't take on building crosswise (contractor A builds floor plan B), that causes complications during execution. The main difference I see is in the staircase location; in the gray floor plan, the upper floor practically starts directly from the living room, while the straight staircase for the green floor plan fits almost a bit tight – actually only if the area under the stairs on the ground floor is left open, i.e. a small shoe cabinet might fit there, but no pantry or similar.

I find the first one on the ground floor nicer and more structured. Both upper floors, however, are not suitable for a household of 5 people. In my opinion, there is too little storage space. Even with 4 people it gets tight, at least the children's rooms are sufficiently large for wardrobes for clothing (seasonal) and sports. I also cannot imagine a bathroom of about 8 sqm for 5 people.