Australia is in the Asian Federation, so yes, there would be a clash with the rules there. Of course, it's worth bearing in mind that Asia has three different CL variants, based on how "developed" each country is, football-wise, so a club in, say, India wouldn't be a problem for a while. It's also possible that the AFC would be willing to agree to waive the rule, though I can't see UEFA or CONCACAF doing so.
A South American team would make sense, though hopefully there would be no attempt to include the name City into any club taken over, as I can't see the South American fans taking that any better than Europeans. There's also talk of buying a club in Portugal, presumably which would require that club to only enter the Europa League year-on-year. That said, given the domination of the Big Three teams in Portugal, that might not be a huge issue.
Of course, I think we should be open to the way that this is all moving very fast right now. Just because the CFG acquired two new teams in the last 12 months does not mean things will continue apace. I heard rumours of a world network of clubs even before NYCFC was announced, but the speed of it all surprised me. These deals can take a long time to do. I wouldn't be surprised per ce if a new team was acquired over the summer, but I'd be equally unsurprised if there was no new movement for another 2-3 years. Mansour and Khaldoon are long-game players. They don't rush things.