So now we have everything from tiny to megalomaniac, it's not so easy to create something productive from all this input.
I haven't read it that way in the last few pages.
Tiny rooms and the requests for the budget are somewhat megalomaniac. There is no contradiction in the posts there.
I find it completely legitimate to plan for 2 children's rooms. No building couple who plans 2 children for the future will be reprimanded here. So I would plan with two rooms.
But if it fits with one for now anyway, then you can also use the second children's room as an office or guest room. If a second child actually comes, then the guests just practice doing without an adequate double room.
The wish for an alternative bedroom on the ground floor in case of illness is also legitimate, but let's be honest: a cast leg, a broken toe, or a hernia can be very well nursed on the sofa. I can't think of a situation where I would have wanted a sickroom during my 4 illness cases in my house. I made myself comfortable in the living room with Netflix and co and sent the kids to bed early.
Double beds in teenage rooms are not necessary either: how great and cozy was the time in a 90-cm bed for the first "approaches" at night. And if a 90 fits, a 100 also fits. That is the fair compromise for a room that you have to share with siblings, because you survived childhood days like that.
However, I see a 10 sqm dressing room as a real waste of space, that can be done well with 5-6 sqm including shoes, and then enlarge the two children's rooms. In this case, you could subtract 1.5 sqm for the sloping roof, but this also applies to the children's rooms! And 10.5 sqm for children's rooms is already somewhat mean when planning a 160 sqm house. The guest room has it better there.
Friends of ours once said: they would rather do without expensive gables and not build the house straight but rotated/across, so it looks more interesting and the garden is more pleasing. They are right. It doesn’t cost a cent more.
A couple in the neighborhood planned 2 children, none came. Only after the pressure after the house build eased, did four children come one after another. They partitioned off the large living room in the open-plan area as a bedroom, upstairs there are now three children's rooms instead of 2 + bedroom, and the attic is being converted. They wouldn’t plan anything differently if they could. Also no bathroom on the ground floor instead of a toilet. It is good the way it is because they are blessed with children. And they also have a dog, even without a shower on the ground floor.
By the way, what you are currently planning is a 7-room house for 3 - I think that opens eyes a bit.
Because just as an example: Heinz von Heiden Hausfinder offers houses from 3 to 7 rooms in the search - but then they are two-family houses.
I would try to get by with a captain's gable. That would rather be well placed in the south. There the two children's rooms. Bedroom above the office/guest room on the ground floor, stairs in the north then. However, make sure that nice areas arise such as the living room being well furnished. The stairs won't work well like that. And the hall closet is currently only good for silk scarves, there must be more space (ideally at least 60 cm of running meter per person).
I think has already optimized this quite well on the last pages.