Final floor plan planning - Rose-colored glasses

... everything is still as it was, only details in the course of the interior walls have changed. It remains a Frankenstein-like treehouse that misuses and overshadows a house with a partially removed ground floor ceiling as building ground – in other words, a stillbirth (and accordingly my hope that the district office will prevent this foolishness). This has nothing to do with rose-colored glasses anymore; you’d have to have had a Magnum cup of LSD for breakfast! If I were the head of the building authority, the building application would immediately be forwarded to the family court for the appointment of guardianship for all involved. If you only look at the floor plan of the upper floor here, you might hardly understand my words – only those who look more closely, especially at the demolition plans. But anyone who looks at the whole story including the existing house in the original thread can hardly seriously doubt the mental confusion as the seed of this crazy idea.

Well, what else is the seller who gets a commission on every bathroom going to say.
I'm not saying it can't be done, but it's certainly not enough.
I have a small bathroom, maybe 6 sqm. That's bearable, but not exactly nice. If the room were halved...

"Rose-colored glasses" in your title fits quite well.

Correct. He is really nice in person. By the way, also here.

This is quite possible even for laypeople, you primarily just need to think of the shown floor plan "in color excerpts": the yellow crossed-out area is the demolition, the gray the sparse intersection between old and new, and everywhere the exterior walls protrude in red like the fingernails of supermarket cashiers, that's where the treehouse squashes the existing little house flat and turns it into a dark cave. It's easier to follow in the original thread, but even here it can be seen that probably Eulenspiegel is spurring things on. The practically downward-open gallery staircase, attached like a fire escape, gives the marketability of the existing house the rest. Not as a mercy, but as a treacherous coup de grâce, mind you. The poor parents would take a rope already during the shell construction if they realize what they signed off on, because on one hand the dear little daughter wishes this so much and on the other hand they believed they could grow old in their familiar environment. But as I said, I firmly believe that the otherwise so often criticized bureaucratic horse will pull the emergency brake.

You didn’t explain in the last thread why your parents-in-law don’t want to move upstairs.
You say they don’t want to expand, so it would be clever if they moved upstairs. Your husband’s office could remain upstairs, since it’s outside the apartment.

Can you please upload all existing floor plans?

It doesn't look like a treehouse at all. Google "Kitzbühel Chalet" to get an idea of what it could look like.