It depends a bit on the client. While it's true that a new .ca domain will do better in Canada than a new .com domain, a brand new .ca may not do as well as your established .com which already has some authority. What we've often done was to setup a structure of www.clientsite.com/ca for the regional site. You can register www.clientsite.ca and 301 redirect it to to the subfolder.

If you do that, you can handle it in WT by creating multiple entries for the site, not declaring a region for the main domain but creating separate regions for each subfolder.