How many others have made the same change? The ideal solution, if it can be arranged, would be for all to be covered by the same approval, including future door-installers. Unless there is something unique about your door, the EC should either try to have all doors removed at the same time without discrimination or support a motion to have them all approved at the same time.
I think you might need to enlist the other door-owners at first and then as many other owners as you can find to support a generic approval. The other door owners might help you by enlisting the owners they know and get on with. It can be presented as an attempt to retrospectively do the right thing for all doors. If you get a very healthy majority in favour but the motion fails (say you get 70% but not 75%) you might then apply to the tribunal for orders to give effect to the failed motion. IE They can declare the motion passed if it would have been reasonable for it to have passed.
On that last point I am assuming the tribunal in NSW, or whichever state you are in, can do what the ACT tribunal can do. That is, it can give orders to give effect to a failed motion, if opposition to the motion was unreasonable. Note, that has been interpreted at the ACT tribunal to be a test of the merits of the motion – what would the reasonable outcome have been? – not an attempt to see inside the heads of the people who voted ‘no’ to see if they were personally being reasonable or not.