Here's another suggestion, make chunk loading be interface way, just how you load with your local client.
Remove the physical chunkloaders, keep the 4 slots limit that you can chunkload.
Each slots gives you the actual 25 chunks to load (just how it is right now)
Increase your slots with real life money or by some high "$" ingame.
By doing this you keep the fairness of having a start up chunk slots that you might deem necessary increase the more invested you become in the server, you also keep away the "forced" pay (that really ticked me off on several other servers, don't force people to pay for the server but give them a home that they would like to donate and contribute on keeping it going).
This way you guys can get rid of the annoying problem of refunding lost chunks and focus on improving other things.
Cheers