French balconies on 17cm Ytong + 12cm insulation?

No, there wouldn't be a thermal bridge there but there are systems with thermal separation. I am more from the awning and sun protection field and with Ytong I always go completely through the wall. There's nothing to be done with dowels there. And there are very good thermally separating fastening systems. And if an awning holds there, your parapet will hold solid as a rock too.

The alternative would be to take windows with a fixed bottom part :rolleyes:

It just does not look nearly as nice as floor-to-ceiling windows with a French balcony.

True! Not just nice, but much nicer. I really don’t understand now why grilles or panels as a balustrade in front of floor-to-ceiling windows are supposed to look better than floor-to-ceiling windows that have a cross frame in the middle or at 80 cm height. And if it’s going to be difficult with the costs anyway, I wouldn’t hesitate for a second and would forego mechanical attacks on the ETICS and plaster.

Since I don't want to give up floor-to-ceiling windows on the other side.

Floor-to-ceiling windows on the upper floor are already out again. Regular windows, preferably wider, offer more space for placing items, don't require privacy screens, are more affordable, and look more harmonious from the outside.

See if your roller shutter manufacturer offers fall protection made of glass. They can integrate it, it then sits under the rail and your wall is left alone....

Good idea, I'll ask - thanks!

Right! Not just nice, but much nicer.
I really don’t understand why grilles or panels as balustrades in front of floor-to-ceiling windows are supposed to look better than floor-to-ceiling windows that have a crossbar in the middle or at 80 cm height. And if costs are going to be a problem anyway, I wouldn’t hesitate for a second and would forgo mechanical attacks on ETICS and plaster.

... is probably a matter of taste in the end :-)
We currently have (rental apartment) floor-to-ceiling windows with a French balcony and find that quite pretty; also being able to open them fully is pleasant.

But of course, costs will be an issue in any case – fall protection with a steel console underneath was briefly estimated at over €20,000, at which point we immediately said, no chance (especially since, as mentioned, it was *actually* already included in the price...).

For our project: We have requested the price difference between a fixed base and a French balcony and will decide afterwards. I would probably use these Fischer plugs for the mounting, as there is no new thermal problem and financially it is not a disaster (-> price comparison page).