I also agree, being able to swap around factions would be a great addition.
The issues that Tifosi 92 mentioned are valid - I've experienced the same issues trying to casually swap them around. Sometimes it works with caveats - specifically, Ally/Enemy models that are used for Snipers will bug out horrifically or produce that goofy looking "FX" text. Any other model that is used, besides the Snipers, seem to work fine as is. Changing around the "environment" line doesn't seem to do anything to fix the issue, but I figure it's more complex than that.
Maybe switching around factions will be a possibility in the future, or not. C'est la vie.