Well the NFL currently has 32 teams, probably too much of a stretch for Australia, but 24 teams not out of the question, we have growing regional cities that could do with a team.
An additional team in NSW, an additional team in QLD and maybe 1 additional team in Perth's or Adelaide's burbs couldn't hurt (Perth and Adelaide both get high enough attendance rates for another team) and then whack a team in the NT, or move a couple more Melbourne teams elsewhere, I am sure North Melbourne would not mind a fresh start elsewhere.