I'm not really sure there's a good answer here. Fuel tax is 43 cents a litre. Australian cars right now avg about 13.1 litres per 100km. So you're looking at ~$5.6 per 100km for fuel tax. This tax is adding $2.5 tax per 100km for electric. Right now, EVs are absolutely creating an regressive tax situation with regards to fuel. Those who can afford to buy newer, efficient cars can usually save money on tax over those…
If you want to tax fairly based on road wear, you have to tax by axle weight to the 4th power * distance driven.
That said, there's a pretty simple solution that doesn't send the same "we are punishing EV owners with an extra tax" message: have a road usage tax for everyone, and slightly decrease the fuel tax.
But please, PLEASE, keep most of the fuel tax. Climate change is a real, urgent issue, and everything that encourages change away from fossil fuel should be kept.