With regard to what is attractive for potential tenants, I would - keywords including dressing room and terrace - not "structurally prejudge" too much what one might prefer for own use and/or weight the proportions of the rooms in relation to the total house size unusually.
My advice (as often before, but especially here): find a good architect who has done this kind of thing several times and has therefore dealt with the responsible building authority (successfully!!!) several times.
The architect - a Muthesius student, as I immediately thought - has apparently built quite a bit locally. So a local architect might have dealt with this several times.
But actually, I'm not a fan of slanted walls ...
Neither am I, and I believe: here one will probably not choose that as a favorite way for reasons of statics either. I firmly assume wooden floor ceilings - accordingly a lot of sense in walls standing directly over each other, and some connection also with the roof structure.