It would be good to be able to open a window on a higher floor of a building without breaking it, and making a ledge or a balcony their to snipe from. You could also make some small walls to take cover behind.
Seems a bit useless to make a balcony if you already have a window. I understand the larger shooting arc, but I'd assume a few of the higher class buildings would have balconies anyways. Plus making a balcony would be very rickety. xD