Hello,
I have the same situation. My property is located in a commercial area. I have living and office space in one building. Since I don't have to move any 'heavy' things, the living area is on the ground floor and the office is on the upper floor. The access is arranged so that I use the staircase as a separation. I have two entrances to the living area on the ground floor because the reception is on the ground floor. On the upper floor, I have three rooms with an external bathroom section in order to have maximum flexibility. Later on, I can redesign all this with minimal effort so that it becomes either a pure office building or a pure residential building. The layout is also designed so that with little effort, the living area on the ground floor can be divided into two apartments. The office on the upper floor could also be converted into three apartments. For this purpose, the necessary 'wastewater pipes' to install bathrooms and kitchens accordingly are provided in the building.
The additional costs for this flexibility are limited if it is considered during the planning stage.
And what will be in 10, 20 or 30 years, nobody knows anyway.
Regards Thomas