I would also be very grateful if you would tell me your idea of how you would plan something like this.
Not with your ideas and wishes, which wrap around a sensible planning like a corset.
It is certainly understandable to have wishes. But they must also be feasible and really make sense. Sometimes you have wishes that you forget again when it works very well differently.
Basically, you already have a small problem with the orientation, but that is doable. It will be more difficult to integrate an adequate granny flat (whether with passage or without) including parking spaces into a city villa. I would classify the possibility of a passage between the units as a nice-to-have, but not important. More important, when weighing up, is privacy and each having an entrance, rather than having to enter the granny flat through the living room of the main house at some point because there is no other way. The outdoor area should also be privatized.
Furthermore, one should reconsider whether the garage, which here is taken as the central point (access to the main house, access to the toilet, corridor to the garden, sauna...) may still be a garage at all and not an additional second corridor.
A garage is for one car. It may be amusing and sometimes practical to be able to go to a toilet from the garden, but completely unnecessary. I think you overestimate the dirt you get from the garden. That may be the case in the first two years, but otherwise, one behaves quite civilly even in their own garden. Besides, after showering, you want to put on clean clothes, and then you have to go through the garage, the garden, or the whole house to get dressed. In 5 years, no one will want to use the toilet anymore because it is forgotten in everyday cleaning and vegetates with the sauna in its expensive existence. What friends have also does not have to be practical—that may be nice for visitors, but you should reconsider if it fits your own everyday life—and the budget.
I will now digress to your budget, which we do not know. For a detached house about 180-220 sqm, granny flat 70-80 sqm, roof terrace, podium staircase, front entrance door in the middle of the house with small lateral projections and the door therein recessed towards the back of the house, so edges, niches or bay window, sauna, probably a children's bathroom for 3 kids, granny flat certainly preferably also with tendency towards barrier-free design... we are somewhere in the range of 600,000-650,000. Added to that are the outdoor facilities, garage, painting work, and flooring. I do not know whether the incidental building costs are added or included in the lump sum calculation.
Main house with 2 full floors and a hipped roof and to reduce costs a flat roof on the granny flat and the garage.
oops:
With that sum, but also with planning an integrated granny flat, you go to an architect!
I do not know if you are calculating in this direction, but I think costs should be saved with straightforward and practical planning in order to possibly separate the two living areas later if one (unit or both) should ever be sold. That does not mean you have to forgo sauna with outdoor area, roof terrace (who needs a roof terrace if you have a garden to maintain????), third shower, etc., but the focus should be on the main living space first and foremost and not on the passage from the garage to the sauna. That honestly comes last.
Suggestions for your wishes:
If possible, sauna with shower-toilet and guest room on the ground floor can be combined. You also do not have to go out of the sauna, but if everything is located at a corner of the corridor, you can go out there or from the guest room. However, if you believe that after building the house there will be so much snow that these considerations are worthwhile at all, then please think yourself about how often we have snow up here. But you can also, if the roof terrace can really be planned, place the sauna on the upper floor, possibly accessible from the bathroom?!
About the playroom: do you have that now too? I must be surprised: with us, parents no longer even go to the playground but let the kids play in the living room so they can do something in the kitchen or at the ironing board during that time. Children are either too young to leave alone in the room or too old because then they do not want to anymore. You planned nice children's rooms, and they should also be used.
If you still have time for editing (EBV), I envy you: I, without children, hardly have time besides my job, house, and garden to do anything time-consuming like editing—but you are right: an office is needed and a guest room for up to 20 guests per year. Maybe you can plan a large play and computer room? Just an idea. Then it would also be suitable for a bedroom...
So: turn off your computer and buy a 100-sheet squared pad. With it you make sketches where what could be. You should always have a grid in your mind, water pipes and heating relatively central, staircase according to the sketch grid as the next step.
Pick up 's suggestion and set two garages as separation. Behind it could be the supply. I would locate this complex quite far to the east so that a forecourt arises in front of the garage from which at the top of the plan a level for the parents and at the bottom of the plan the access to your city villa is created. In your garage, you can then put utility room, sauna and shower-toilet, office/guest SE, etc. in the house...
You can basically plan a semi-detached house where one party does not have an upper floor but the other gets this area on the upper floor.
Room program for architect for detached house:
Kitchen, dining and living room, kitchen with sliding door
Storage room, utility room on the upper floor, possibility of passage garage/house
Sauna
Guest/office or play/office
Bedroom with dressing room (not trapped)
3 children's rooms
Bathroom
Roof terrace if possible
Open to the southwest
Good luck