Dear Client,
I am proposing 2 options for functional disposition for ground floor.
Maintaining 3 rooms on ground floor (future bedrooms or similar) and 2 bathrooms (+ laundry, + existing garage, +living area)
I think there should be two entrances (when you separate upper floor front entrance will be only serving, and side entrance (near garage) will became main entrance for ground floor.
Hope that this solution meets you requirements.
Best regards,