Is it possible to build a balcony without scaffolding or street access?
Your plan has some far more serious considerations than just the change of looks, approval of the neighbors and building activity access. You cannot just hang a two meter wide balcony decking on the side of the building without some careful engineering. 

Support legs for the outer edge that go to the ground or large angle braces that would attach to the side of the building above or below your floor are out of the question for obvious reasons. This means that only remaining possible option is to use a cantilever design where the deck support is provided by beams or timbers that project over the outside supporting wall of the building but then tie into the floor structure a good way back inside the building. For a 2 meter projection outside you would be looking at a good 4 meters or more of beam or timber length inside. 

Whether the cantilever design would even be possible would depend upon many factors:


Does the outside wall have sufficient structural strength to support the cantilever beams? Particularly considering the ceiling height windows below.
Could you even open the outside wall up enough to make access to poke out the beams from the inside?
Is the building floor construction even allow for tearing it open for beam insertion? Some brick buildings have concrete floors.
Even if the building has an internal wooden structure for the floor joists are they parallel to the outside wall? If so then inserting cantilever beams is basically out of question.
Remember that your floor is the ceiling of the neighbors below. If you start to tear into the floor it is pretty hard to believe that it would not require some pretty serious cooperation and disruption of the neighbors.