I’d call BS on the committee member. Legal aid only helps persons , not body corporates, and only for criminal cases.
In any case ask for the written advice from legal aid. Bet he cant show it.
What did the tribunal rule? Does it matter who builds the screen? If the tribunal has ruled the screen needs to be built and it’s on common property, the OC has to do it in reasonable time. Let them deal with council and builders.
If it is common property it’s the choice of the OC in terms of materials and design.
If you want to do it to your design, and you want to pay for it, then you will need a bylaw.
That’s another can of worms.