Since you no longer write anything about the floor plan itself,
That may be because interested parties of the Floor Plan Discussion section are not addressed in that subforum
you can also wall up the access door between the garage and utility room and later enlarge the WC and add a shower.
Do not underestimate the arbitrariness of the technicians: craftsmen like to use the entire width, so there will be no space left for a shower later.
Well, I think in an emergency some wonderfully narrow room will be cobbled in somehow...
No, due to the lack of ceiling height, emergency exit window, no habitable room is allowed anymore, and therefore the ceiling will probably be constructed in such a way that no spacious living room can be developed there. My tip: I would rotate the shape of the guest WC and then place the washbasin on the left side of the plan and the toilet under the window. It is just a suggestion for more finesse if possible. Then: we have a similarly designed office (basically a similar floor plan anyway) I find the layout somewhat annoying with the door in the "narrower part"... I would turn the staircase, make the storage room a cloakroom, make the office rectangular and have only a small storage room from the kitchen area on the left side of the plan. Upstairs I find the situation of the bedroom as a double passage room doubly suboptimal... that could be changed better - anyway by turning the staircase. The children's rooms would also shift somewhat, but I think that works. But of course, it does not have to... is just a suggestion.