If/when you get a postcard/spam email that you're included in a potential class action lawsuit settlement, you can opt out of the class (in which case you preserve your legal rights to sue separately) or file comments with the Court.
You can, but then you lose the power of a collective and have to manage a lawsuit yourself. If you are being represented as part of a group, then you should have means to direct that representation.
Surely some firms choose to hold referendums already, but I could see that being a good law! As Better Call Saul explored in its early seasons, the interests of the large law firm can easily diverge significantly from the interests of the plaintiffs.
With some coordination, perhaps enough people could opt out and start a new class action lawsuit.