I don’t think there is anything wrong with an OC reaching an agreement with someone to use part of the common property and charging for it. In a lot of scenarios it makes sense and everyone benefits.
On the subject of who owns the common property, there is a very fine distinction. The individual owners don’t own it, the Owners Corporation (a legal entity) owns it and effectively holds it on trust for the benefit of the owners as a whole. While this may seem like splitting hairs it does make a difference. We had someone who moved in a while ago who started demanding to be allocated various bits of the common property for his use, stating that it was communal property and he had a right to use it in that way. We had to tell him that that was not the way it worked. As he wanted to be given exclusive use of a part of the common property that was used as a thoroughfare by everyone else, we said no.