Yes, often members of a society take matters into their own hands and commit illegal acts such as enclosing balconies or even converting residential premises into commercial premises. Doing so without the proper permission is an unlawful act and very often it leads to conflict with angry society members and civic authorities alike. However, there is a way to legalize it. members of a society who want to enclose their balconies have to make an application to the Ward Officer along with a copy of the plan of the balcony. The applicant has to pay the prescribed fees for the same and if the applicant has already enclosed the balcony then the ward officer has the power to regularise the case on receipt of the application. The Ward Officer will prescribe the penalty and the same will also have to be paid by the applicant.
No, it is illegal and definitely it will spoil the appreciation of beauty of the building and you should not do any modification unless the society members agrees for it. If it is a safety issue, many other residents would also have similar problems. So try to push your points unitedly with others for positive outcome.
I fully endorse the views expressed by Mr Piyush. Each RWA has bye-laws governing all aspects of the admin in the society premises. there is an elected managing committee to look after the day-to-day running of the society. in addition there is an AGM where all the association members gather and take decisions which effect the society and its residents. I feel that you should apply in writing to the MC regarding this issue and request for its inclusion in the agenda for discussion. in case you do not find any favorable decision in the MC meeting and the proposed modification is not in contravention of the bye-laws of the society, then you may approach the District Registrar of Society for necessary action in the matter.