You have clearly described your situation, and yet people don’t know you well enough to recommend what is right for you. Without children in tow, however, you can wonderfully arrange things freely and alone according to your needs; the "normal" residential house always has to cover many current and future scenarios for multiple people. You don’t have that and should therefore use it to your advantage.
I can also imagine your house being built in wood, rather modern, with open-concept rooms featuring large glass surfaces on the sunny side, a central fireplace or masonry stove, and additional heating (infrared and/or air conditioning). For example, we live as two people (I am usually at home during the day) in a house with a lower energy standard than KfW40, and we did it that way, far from common calculation models, and it suits us wonderfully.
Depending on my mood, I light the fireplace, and adding more wood is more a pleasure than a strenuous task for me. So, most of the time we heat with the stylish fireplace that we bought used online for 20% of the new price (plus 250,- transport + 500,- assembly). Since we prefer less heat, we treated ourselves to an air conditioner, which I would always do again. If it is ever too chilly for me in the morning, I switch it on briefly, and after 15 minutes it’s nicely lukewarm, and from 9 a.m. the sun usually already warms the house through the large windows. In addition, we have infrared glass modules embedded in the ceiling that could heat the entire house but are almost never used. They are not expensive (partly also bought "used"), look stylish, and could be switched on briefly if really needed.
With three children, a different life, a different room layout, and two full-time jobs, I might have done it differently, but as it is, it works wonderfully for us. Photovoltaic power in summer mostly contributes something for our electric cars and then also for the slight consumption of the air conditioner.
What I want to say is that in your situation you can free yourself from some (expensive) things because no one in the room complains that it is too cold/warm or that the DSL signal is too weak or the bathwater is not hot enough, etc. You know yourself best.
I would create a super beautifully designed workspace for myself, a rather compact kitchen (not too large), and a small living room (with or without TV orientation). I would want to use the resulting attic as a possible expansion reserve for 1 room, in case Richard Gere happens to pass by on the way to Lago Maggiore, storage and/or a technical room, although you might not need so much usually space-consuming technology and it might already fit on the ground floor.
I have not tried it myself yet, but for such an application, electric instantaneous water heaters seemed extremely sensible to me, because you don’t have to keep large amounts of hot water ready, and when you need it, it is nevertheless immediately there. Added to that is the generally important point for me that these things are easy to operate and maintain.
I would actually insulate the house to the maximum (at least KfW40), because then you can live in it for a long time without heating at all or only heat spotwise, since such an insulated house does not cool down that much.
While reading through this, I unfortunately recall only a few truly special houses but do remember, for example, the info and pictures from . They stand out to me as a high level of taste and functionality with a low amount of pre-chewed, expensive pseudo-luxury.
There, as also with us, a solid wood plank floor was installed (also cheaply bought and delivered online from a carpenter); that is something that perhaps a friend or an existing all-rounder could simply help you lay. I would also have no problems installing it in the bathroom; in our house, which we laid ourselves, it’s even in the utility room. I even once saw a stylish living room floor made of OSB panels, so there are possibilities to save money here and spend it elsewhere in a way that suits me. I would rather be on the bold side there.
Regarding a gallery, it is naturally super beautiful, and I would not let it slip away from me just because of the killer argument "window cleaning" if I liked it; you can maybe estimate possible additional costs during planning.
I think, starting with a truly individual floor plan for you and the search for a suitable house builder, this can become a really beautiful, special home. If you figure out for yourself which of the current, often expensive "must-haves" you actually don’t need and can save on, on the other hand you can financially manage certain special things for yourself.
Therefore, I would invest maximum energy into my matching floor plan and also consider building as few fully enclosed rooms as possible and rather think of ceiling-high room dividers, since you are alone. It doesn’t have to be like in a great holiday home in Morocco where even the toilet was only half-closed, but maximum openness would be my theme here. This would also have advantages for the necessary ventilation of the nowadays obligatorily airtight building envelope.
These ideas do not necessarily have to suit your taste and are only meant as a possible impetus on how it could also be, because floors, bathrooms, heating, kitchen, walls + doors simply devour money, which is why it’s better to check the actual need for them once more.