Going by existing SC locations, the Moe/Morwell/Traralgon region is an ideal location so far as distance between superchargers go. (~150km) and is on the main highway. Bairnsdale an obvious second hop.
Of course they could just as easily select anywhere Warragul-Sale-Orbost. The Warragul location could even be skipped, it's only 211 km from Melbourne to Sale, and then they could backfill later on with a site in Dandenong, Pakenham or Warragul. etc. Dandenong is pretty close to the city but it would be a good top up location for not only Gippsland drivers but also Mornington Peninsula and Phillip Island.
Also have to consider what locations are viable on the other end (NSW South Coast). If there is a big gap with no reasonable services that would limit all the other sites.