A QS report is simply a surveyor doing it for you. You could put it together yourself using the ATO resources, but then you'll need to be able to value everything.
Given the benefits, there's no real reason why you wouldn't get a QS report.
This is all about how to calculate capital gains. If it's CGT exempt after 5 years as an IP (such as under the 6 year rule), then there is no capital gains. Depreciation addback isn't applicable.