First of all, it’s great that you are thinking about what you want.
Now, in my opinion, it’s not really possible to plan “generously” on 140sqm anyway.
I’ll try to mentally compare this with our semi-detached house. We have 145sqm but with an expanded attic and approximately 7 x 12 meters.
Since you don’t have children yet, you obviously can’t take some things into account, and naturally, you can manage with your floor plan as it is. But if you have the chance to build something new, it would be wise to do it as optimally as possible. Sooner or later, you’ll often find details that you should have done differently.
I’ll try to list the problem areas of your plan:
Upstairs:
I would make the bathroom large enough to fit a double washbasin. If it works out with the two children, that would really be sensible. And I would move the bathroom to the upper right corner, so both children get rectangular-shaped rooms. Also, then you have a partition wall for a wardrobe.
Are you allowed to build dormers? That could create even more space.
The light blue area probably extends up to the 2-meter line?
I find the children’s rooms very unfairly small compared to the parents’ area. When they get older, they’ll also need space for proper wardrobes (for small rooms, a dresser is enough). Where should those go?
What is in the empty space behind the L-shaped wardrobe?
Downstairs:
The aim of minimizing hallway space is commendable, but with two children, it’s not practical.
On the current plan, I see the right side of the door filled with shoes, the left side with a few hooks for current jackets, below stacked bags and backpacks (or vice versa, doesn’t matter). Where will the stroller go? (Alternatively: a storage area for everything you temporarily place in the hallway: groceries, parcels, ride-on toys, stubborn children you have to step over ;) Visitors you greet or say goodbye to).
There should be a built-in cabinet under the stairs, but then it won’t fit together with the passage and the utility room door.
And a large cabinet on the left is not possible because you wouldn’t be able to walk up the stairs comfortably anymore.
I find the shower bathroom downstairs again too large (compared to the other rooms).
The utility room could work; what should go in there? Washing machine, dryer, supplies, service connections, water heater?
What kind of heating do you have? Maybe cut out a window or replace it with a higher-placed window strip to keep storage space.
I won’t say anything about the living-dining area; others have a better overview there.
Of course, it works as it is, but with so much money being invested, it would be nicer if it were more than just “it works.”
And then please fill out the questionnaire so that it can be optimized better :)