So it comes down to whether the Meeting that you didn’t attend either personally or by granting your proxy, with instructions, to an Owner who was attending was a General Meeting of the Owners Corporation, and whether the Motion seeking to approve of the re-build was resolved as a Special Resolution, where the vote is assessed not on the basis of a simply majority (show of hands) but instead on the basis of the lot units of entitlement of those Owners in attendance, and where ≥75% of those need to vote in favour in order for the re-build proposal to pass.
If it was a General Meeting and the Motion was properly (i.e. specially) resolved, then I’m afraid that it’s not a case of any existing structures being changed without regard to Owners, just without regard to you because you didn’t attend.
If your balcony door doesn’t have a leakage problem, then your best (but not only) avenue would be in my opinion to offer to accept personal responsibility for the on-going maintenance and repair of it. That too will require yet another Motion to be specially resolved at the next General Meeting, and the subsequent registration of a Special By-Law (SBL) covering your proposal (if it’s accepted), so perhaps canvass the opinions of other Owners in the same situation as you with a view to both strengthening your case and sharing the cost of a single SBL covering all of the Lots involved.
As I said there are other avenues, but they’re more difficult and success is less likely in my opinion IF the Meeting was properly convened, the supporting documentation complete, and the Motion properly resolved.