Your terminology is confusing to me; perhaps you use different terms in Victoria. By “Ballot” do you mean a vote to approve the aircon unit?
I don’t know the rules in Victoria, so I don’t know if this is a Committee decision to make, or a decision that the entire Body Corp gets involved in. I presume from your post that the entire Body Corp gets to vote.
Anything that is sent out for a vote should include information about the proposal. Presumably the owner of the lot that wants the aircon will put this together along with information about the trades involved, where and when the work will take place and a statement about why they need it. I don’t see why the Committee can’t correspond with the owners to explain why the Committee thinks the proposal is a bad idea (noise, appearance, water runoff etc).
But a better approach might be for the Committee to work with the lot owner to find a more suitable solution.
BTW in NSW if someone gets permission to instal an airconditioner on common property, they need a by-law. They can’t modify common property without one. And the lot owners pays all the legal fees associated with developing and registering that by-law.