Repairing the balcony with no changes just requires a simple majority motion to be passed, but any changes to the design requires a special resolution to be passed and so unless the owners can get a 75% vote in favor you are ok.
Even if they did get this motion through any changes to your lot requires your written consent. I’m basing this on the fact that the courtyard is effectively an exclusive use area and changes to an exclusive use area require the lot owners consent.