I just had an idea lol
You have the normal server which everyone can join and doesnt get income.
Then you have a "seperate" server that you have to pay to play on, and have all the perks on that server.
That way you would still be legal because you are technically using 2 different servers, only the paid server is the one with all the cool shizzle. and the servers could communicate to one another regarding player locations, items, statistics and other stuff.
You can thank me later I just saved the pokemon server!
No one would play something like that, really, would you play on a server where donators are segregated from regular players? There's no way to show a regular how useful the perks would be.
One idea I've had for a while that can get around it, giving a random player a 24h upgrade.