The challenge with quotas, of course, is that when women are appointed or find their way through, the comment will be made that it's because of the quota. The big challenge then remains having a really carefully thought-out list of criteria that a candidate must meet. We know there are very many highly trained, highly skilled, and absolutely excellent candidates of both genders. Often, though, as we've certainly seen in the research we've done, it is the unconscious bias that will enter into hiring.
If you had blind applications or names that could be either male or female just to get through the initial stage of application, it would be interesting to research the impact that would have. Then, I believe, you could put a quota in place, and women would know that they had been appointed or that they had been the successful candidate because of their skill set, not because of their gender. Perhaps more importantly, the men who might be critical of that would also be aware that the women at the table are there because they're the best candidates.