If I can butt in on a couple of issues….
The Special By-Law should not be exclusive to your proposal, but rather should apply to all Owners – including to those who have already enclosed their balconies (ideally) and to all those who may wish to do so in future.
For the above reason, and additionally because the Strata Regulators (the Consumer Trader & Tenancy Tribunal in NSW) look favourably upon By-Laws that are advisory rather than prescriptive and/or prohibitive, whatever wording your Executive Committee decides upon shouldn’t prescribe what type of windows must be fitted, but instead speak to features such as aluminium, non-reflective, consistent colouring, in keeping with the facade of the Building etc etc. Like what happens if a product that’s available now, is unavailable next time an Owner needs to comply with a prescriptive condition of the Special By-Law?
IF your Committee (or a Member) has/is a reasonable scribe who can avoid legalese and ambiguity, then there’s no reason why the wording of the Special By-Law cannot be prepared and agreed “in-house”, and be submitted for Registration to Land & Property Information using Form 15CB (in NSW) for the princely sum of $102.00.