In my opinion your assessment is correct. Perhaps the Secretary already knows this …. and wants to do something a bit ‘cheeky’ hoping that no one will notice!
The Motion should be ruled Out of Order unless the second part of the Motion (i.e. the sun screens) is removed.
The Motion contains 2 separate issues and therefore should be separated into 2 Motions.
One Motion should deal with the Maintenance and Repair of the balustrade. The second Motion should deal with the Improvements to the Common property (with voting by Special Resolution).
If the Special Resolution fails then the Owners who wish to install sun screens can always submit individual Motions and By-laws to cover the improvements to common property, and pay for this improvement themselves.
Something to consider when approving the sun shades is whether the sun shades will offend the the architect’s original vision of the development. See here: https://www.lookupstrata.com.au/nsw-sun-shades-for-apartment-balconies/