Installing double glazing is defined as a minor renovation (not requiring a special resolution) under Section 23 of the Strata Regulations. However, it is also subject to the rules under Section 110 (minor renovations) and possibly Section 132B (sustainability) of the Strata Management Act.
In short, I think the committee (if so empowered) could approve this but should demand a binding and continuing undertaking to maintain and repair the windows and doors at the lot owner’s expense and with the proviso that it wouldn’t alter the outward appearance of the block.