Board Thread:Battle Nations Discussion/@comment-71.195.202.168-20130720174611/@comment-4632427-20130721122239

You get access to the Southern Frontier when you get far enough in the main mission sequence. It's possible to get that far by your level, but less likely nowadays than it used to be. Newer shops and housing make it easier to level faster, while missions are just as slow to complete as they used to be, and there are a number of missions that people often stall out on because they demand the construction of impractically expensive buildings.

Basically, you should unlock the Southern Frontier if you keep doing missions. You won't have to do the two missions that require building Nanopod buildings, but try to do everything else and you'll get there eventually. The Southern Frontier doesn't come until after you've defeated Gantas.