First of all, I think it could exist without changing the boundaries, but I don't think that would be preferable. I think that some modification in the boundaries for individual MPs would probably be desirable, but not necessary.
Then you have the regional component. It depends on the split, as mentioned earlier. If you have a 60:40 split between MPs and the regional representation, that could lead to one kind of size recommended for ridings, as distinct from having a 50:50 split. This could result in different-sized constituencies.
It is complex in terms of getting it established and sorting it out. When the committee sits down and looks at some options, to be banal and state the obvious, you should consult with some technical staff people who could guide you. If you agree on certain principles, such as MMP, then look at the variables within that system and what they would imply for constituency size and so on.
I hope that answer helps.