Could you provide a Centralized Banning API? Rust Wiki: Centralized Banning
This will allow unmodded/vanilla server owners to get a great list of banned users.
You could also provide an API with multiple parameters like:

https://myDomain.com/api/rustBans.php?VPN=false&maxGameBans=2&maxVACBans=1&...&steamdID=

Currently there is an API, I will add support for rusts requirements 

It's been a while, but avail now https://serverarmour.com/centralized-bans