I think you would need at least provincial regions for top-up, or perhaps smaller regions within the provinces. You wouldn't need to adjust that with P.E.I., for instance, but you might in Ontario. Part of what I like about MMP is that it does give you the flexibility. Folks are fond of saying we need a made-in-Canada solution. I think there's enough room in MMP that you can design it to fit the federation well and to respect geography and local representation, which Canadians are quite rightly wed to. I also prefer open lists, which helps address some of the problem of Canadians not wanting too much political party influence.
I'll quickly comment on nominations to those lists as well. Right now we say, “Well, we don't like party lists because how do folks get nominated?” Ask people how they get nominated now. There are a lot MPs who say after they get elected, “Well, I got nominated somehow. I can't exactly tell you how it happened.” If you read the Samara book, Tragedy in the Commons, it's a great story about how these processes are opaque, bizarre, and inconsistent. So I do think we need to discuss also how nomination processes happen, but you can do that within an open list PR.