It depends…….
Are the balustrades obviously unsafe, for example are there gaps large enough for a child to fall through?
Are there other works planned? If a development application is lodged with Council they take the opportunity to require certain upgrades by way of conditions placed on the development consent.
If you are doing something like a balcony remediation including waterproofing then you will need a design by an engineer before anything else. What is the reason for the upgrade?