nice idea, bit of a puzzle as the pictured target building HAS suitable balconies that would be easier to simply enclose?
and if they dont have a balcony already? then making a door to the plant room is going to be an issue?
The idea seems a great idea, and surely enhances apartment living. However, nothing is said of a simple fact: buildings are designed for a specific Load Factor, and if everyone decided they wanted one of these, the structure will collapse. I would not recommend such modifications, unless there is a concerted study to guarantee safety. If these units have their own foundational strength, perhaps it would work. Decorative ideas can get you killed if not done by a structural engineer.