Simple, just have a weight limit like a lot of other airports have.
Anything under 1500 kg is exempt from charges, anything with an RA-Aus registration is exempt from charges.
They have no effect on the durability of the airport with regards to maintenance but they have a huge influence on People buying fuel, Staying in accommodation, eating at restaurants and using taxi services.
I know back when I was flying a lot I would not avoid, but have a preference for, airports with facilities that didn't charge recreational aircraft.
I am guessing with an overnight stop and fuel and taxis and food I would be putting $400 into the community every overnight stop. 500 of these recreational aircraft every year and it is another $200,000 into the local food chain, something that cannot be sneezed at !
A couple of problems for the airports is that a private company does the planning fee charges for the airport owners. I have heard that if the landing fees are $10 then the airport owner gets only $4 dollars and the rest is going to Avdata Or whatever they are called so, the airport themselves are not getting the majority of the funds. Also, Avdata has a vested interest in charging every movement because this means they are getting more money. Piss them off and make it free for everybody except RPT