About 60% don't have enough of a grasp of the situation to make an informed decision, and those who do will be split between protecting their interests and having a balanced agreement that doesn't favor either group too much. None of that will change by disclosing beforehand or having a say, but if it's disclosed first with a release that both sides agree on, at least it will be harder for those involved to lie about it. Of course they will still lie about it, just like politicians did about brexit, but it will be easier to point out the liars after.