in this design, I use three elements of design as the focus: white colors, stone masonry as emphasis, and arch opening in walls.
I also make this design proposition with as little renovation as possible.
While still effective to fulfill your needs.
We got a dining room, living room, kitchen, and bathroom in the ground floor.
And as you stated this will be for you and our wife's main usage,
I think it doesn't need a formal entrance hall and I use the space after the entrance as dining room - bar.
This way, the kitchen and bathroom position will not need to be changed (and minimize the renovation of utilization)
And for the living room, you can choose a sofa bed for guest's usage.
We got a foyer, a bedroom and a bathroom in the mezzanine floor for your private use.
Because I don't have the exact height and exact curves of the ceiling, it will need a bit of adjustment in the real-time. But I think the design can be implemented with just a little modification.
You should keep the existing curved arch ceiling, and you only need to add flat ceilings for the dining room, kitchen, and bathrooms (if the height can be accommodated).
As for openings, I only adjust two windows in the left side, and I replaced the door with a glass door to make more light comes inside.
I think it doesn't violate the regulation.
What I love the most about this design proposition is the arches in walls, with the composition of colors and textures, I hope it will create a relaxing atmosphere as your holiday home.