And how rentable are damp and waterlogged apartments these days?
Sorry to be glib but sometimes the needs of the many outweigh the needs of the few. This is the basic tenet of unit ownership. Clearly the waterproofing was a major fix, benefiting all owners.
I wonder if you had permission to install the airconditioning units in the first place? They must have been attached to common property – whether hanging on an exterior wall or their pipes etc passing through an exterior wall. If permission was given to install them a sensible Body Corporate would have required an exclusive use bylaw to be registered making them the individual owners’ responsibility – in which case, you are on your own as they are your responsibility.
If a bylaw wasn’t registered and they are attached to common property, there’s an argument that they then become part of common property, and the Owners’ Corporation can do with them what they wish. And that’s what they’ve done.
I also wonder where you were when decisions were being made about the major waterproofing project and the contractor said “those airconditioning units have to go”? That would have been the sensible time to raise an objection and work out a solution.
Finally, think of the increase in value of your unit now this major project has been undertaken. To return to my first point, dry and serviceable apartments are much more saleable and rentable than damp ones. Short term pain for long term gain.