Look, the first principle of a tax system is to find the tax base, what you're going to tax. At the moment, the problem is that we can't find the tax base.
My design for an information exchange system would simply be saying that this person has an account in this tax haven and Canada needs to know that fact. If there were a simple exchange on the existence of the interest in the account, the Canadian tax authorities could then say, “But it's not on your tax return. Why isn't it on your tax return? We need to know.” That's the smoking gun.
About 90% of the benefit of automatic information exchange would come from compliance. People would know that they could be found out if just that information were exchanged.