You could certainly talk to a cabinet maker and have something custom made to your preferences and design style. You could also talk to a closet design specialist who might be able to utilize every square inch of that space more effectively while working with a cabinet maker. Part of how the space is designed will depend on the age of your girls. If they are under 12 or so it shouldn't be too difficult. If they are teenagers, talk to them and find out what kind of space they need.

Please consider this reorganization of the spaces which makes the most off the area available. The dining area is moved from the dark interior to share the same area as the living room, across from the open kitchen counter which would serve as a buffet. The black volumes are false columns faced in stone or marble or any other material of your choosing to give the space some girth. This distribution of the spaces gains you a walking closet for the master bedroom. Its ultimate effectiveness depends on your needs. I hope this is somewhat useful.

Given the very large living area, the USP of this apartment, there are a variety of screens available which can be used creatively, mobile or fixed, see through, translucent or opaque, full height or part, etc to divide the spaces and yet give a free flowing look of a large open space, the light and views from the large windows.

post pictures of cupboard