The one thing with Australia, I'd probably try to highlight the types of roads / ability to set road type preference.
I.E in a small hatchback I'd want to avoid unsealed roads, most rental companies will disallow them in the t&c's + you don't want to get stuck on them. However on a offroad/adventure bike / 4x4 i'd want to find the most remote, gnarliest roads possible.
I'll probably use this to find points of interest / general route then use the Hema 4WD maps to find a more specific / interesting route.
Also you might do well branding / marketing /designing the site for the grey nomads. A lot of them use https://www.wikicamps.com.au/ and pay to use it, they have money to spend. Some cross integration with sites in wikicamps would be useful also.