Variants for furnishing the all-purpose room

1) A couple of friends + child come to visit. Then we sit together at the dining table, and cooking is nicely done on the side in the kitchen.

That happens OFTEN

2) Half the family is visiting, birthday, sit-in, mulled wine party, or something else. Number of people >8: that takes place in the conservatory, which is also easily accessible from the kitchen.

That is RARE The rare occasion, in my opinion, can always be handled somewhat spontaneously and individually; for that, there is the conservatory....... The fact that the "spark didn’t catch" with conservatory=dining room, I would seriously reconsider putting a nice, longer table directly next to such an island/extended work surface. These days you should look at pictures of that. We decided on that and suddenly there is space in the open-plan room. Also, you don’t sit like on a bar stool but are still close to the person cooking.

My problem definitely wouldn't be the space, but that the kitchen doesn't face the main terrace, but that's a matter of taste.

What do you mean by that? That the dining table is in front of the door to the terrace instead of the kitchen?

Which one will be your main terrace? The one in the south or the other one?

That is OFTEN That is RARE In my opinion, the rare can always be achieved somewhat spontaneously and individually, and then there is the conservatory........ I would seriously reconsider if the "spark hasn't jumped" with conservatory=dining room, putting a nice, longer table directly next to such an island/extended work surface. You should look at pictures for that. We decided on that and suddenly there's space in the open-plan area. Also, you don't sit like on a bar stool but still close to the cook.

It's not that rare for us at all. Our whole family including all siblings live here. We often have a full house. But we'll see what happens after Corona and how things might change with a child. But what you are writing speaks in favor of separating the conservatory. What's the point of having a 10-person table there if I usually will sit there with two plus child(ren). That feels strange, doesn't it? With a connected conservatory, I rather have this option space to fall back on. Or am I making a wrong assumption here?

Which one will be your main terrace? The one in the south or the other one?

Definitely not in the south, only three meters to the neighbor's boundary. Terrace and conservatory face west.

I would neither furnish this room with a "wall unit" nor with a "corner sofa" - in that respect, I don't like any of the options. Sofa with its back to the window - stupid. Remove the window for the "wall unit" - also stupid.

Conclusion: Buy furniture that fits the room.

I prefer the table facing the garden.

But now I understand why you are having such a hard time developing the floor plan. You are trying to reconcile too many self-imposed must-requirements.

Only in this way is it right: is thinking about their own life in the house. If not everything works, you can omit something.

With an attached conservatory, I rather have this option area to fall back on.
Or am I making a mistake in thinking here?

No mistake. That's exactly how one can see it well.