Feral animals and other noxious invaders need representation, probably as a bunch of Dark single-and-dual type regional variants. For example, a really vicious-looking Dark type Meowth that evolves into a Dark/Ghost Purrsian, referencing the incredible destructive effect of cats on the Aussie wildlife. Or a snooty and malicious Dark/Fire Vulpix. Dark type Ratatas are obvious, as are Dark Type Lopunny and Buneary.
I can just see a final stage cane toad pokemon that is just this mass of oozing, seeping pus, and is basically the region's equivalent to Muk.
A Rock/Water Pokemon based on the Thorny Devil just seems so obvious to me. Maybe give it a unique Ability that makes it Resistant to Water attacks.
Would jellyfish pokemon based on the box jelly, Portuguese Man'o'War and lion's mane make sense, or are they superfluous with Tentacool/Tentacruel and... Jellicent, I think it's called?
A bearded dragon Normal type just seems so obvious; they're one of the most iconic and common lizards in Australia. But maybe it could also kind of be the region's Magikarp; grind it all the way up to level 55 and it evolves into a big badass Normal/Dragon dual-type.
Would a Poison/Fighting spider pokemon based on the Sydney funnelweb make sense? This is one of the country's most venomous spiders, and also one of its most belligerent, to the point they will actively chase you and try to bite you if you get too close. There's an argument for Poison/Water or Bug/Water, considering they are surprisingly strong swimmers and have even been known to infiltrate homes by crawling through plumbing into showers.
What would a blue-tongued skink pokemon be like?
Australia is known for its sharks, maybe there's some shark pokemon? I can see a Great White pseudo-legendary Water type, and a Ground/Water or Grass/Water wobbegong pokemon easily.
...Can anyone else see a pseudo-Legendary Water type based on the Murray River Cod?