Good thread, I find that whenever these are posted (on social media) people just list places near themselves, or go straight to the ridiculous ("build stations across the Nullarbor" - not that such a long term plan isn't ridiculous but look at existing coverage - they're obviously not at that point). It's nice to hear suggestions that reflect a reasonable rate of growth and breadth of coverage.
One area that I'm surprised isn't covered more in WA. I know that any new location in the eastern states has a multiplier effect on the rest of the eastern network as a whole, so it's a lot harder to justify in WA. However had they progressed at a faster rate initially, the entire south west (South and West of Kalgoorlie) could've been built out by now. In any case the Perth-Bunbury-Albany triangle is a good target for end of 2023, as well as site at Northam and Brookton (sort of a hub-and-spoke layout around Perth).
Port Augusta is an obvious one. Perfectly spaced from Clare, home of some progressive organisations in the renewable space, and not only does all the traffic heading from the south-eastern states to Darwin and Perth pass through, but also the Eyre Peninsula and the Flinders Ranges.
In Victoria, Ouyen or Sea Lake would be ideal to serve both traffic towards Mildura and some Adelaide/Sydney cross traffic, as well as Mt Gambier (SA)/Hamilton the south west.
Of course I was going to get to Tassie

The main highway here is best considered as a regional route south of Melbourne in the same way as the Princes Highway east and west of Melbourne is. Evie Networks have reported that their 350 kW site in Campbell Town is the highest utilised of all their sites nationwide. Electric Highway Tasmania has reported that about 30% of the vehicles using their sites (which notably are NOT on the main highway) are interstate vehicles.
East Devonport, Campbell Town and Hobart are ideally spaced (gaps of 146 km and 133 km) for those coming off the ferry and travelling to Hobart. I would suggest a different location than Campbell Town for the central stop (just for variety, with Evie) but there really isn't a town in that region with as many facilities. Campbell Town is also great as it gets those stopping on the Launceston-Hobart route too.
One thing that there hasn't been much talk about is duplication of the Melbourne-Sydney-Brisbane route, as well as rollout of V3 sites. My prediction is that the first V3s will appear on this route, about 250-300 km out of each city. Or to put it another way, we may see V3s in Wangaratta, Yass, Bulahdelah... (and Maclean/Harwood fits the location for the route out of Brisbane but obviously that wasn't V3). This isn't because of traffic volume, but if you look at the vehicles capable of the V3 speeds, and their longer than average ranges, these locations are perfectly spaced to do Syd-Melb or Syd-Bris with 2 short stops, and the fact that they are between existing sites means they are good backups for any of the others should they be busy or unavailable for any reason.
The spanner in the works, as others have mentioned, is the rollout of Evie/Chargefox 350 kW sites. If they are building these, and for all intents and purposes they are as good as a supercharger, why should Tesla build superchargers in the same area?
That's my brain dump, time for bed!