While it would be nice to have some physical separation and do something in Kitchener, London or Windsor, the place that makes the most sense is Mississauga.two more teams in Ontario? where? an additional Toronto team is about all I can see.
It's the 6th largest city in the country, has a large corporate base, is basically smack dab in the middle of the 7+ million people in the Golden Horseshoe, will not have players and media types living and working in what they perceive to be small towns, and has several plots of land that could be feasible for a CFL sized stadium.
I'm not sure if the Argos could share that same "suburban" stadium - a la Giants/Jets - but on its own I think the Peel region could easily support a CFL franchise, as the market is both larger and wealthier than a few of the other in the league. It would be the first big time sport in town and the one team that puts Mississauga "on the map" so to speak, which I think a lot of people would rally around, including much of the local corporate base.
The stadium could be soccer friendly and maybe allow for an NASL team to share. Who knows, but it has seemed odd to me for a while that there is so very little talk of pro sports here. It's one of the few things that could help change perceptions about what Mississauga is, IMO.