I was thinking of a command that could be applied to donators and you can decide on what dollar donator could get it, but here is my idea.  I had a lot of strick in my inventory and I had to keep putting it in my conversion box to make it wool. To make it easier I was thinking, if there is a way to do it. I am not a programmer so I dont know if it would be possible or east to do, but make a command called /convert and it automatically converts the items in your inventory to the other item if it has an option.  Ex.  If you had 4 stacks of string in your inventory and you did /convert it turned it to 1 stack of wool.  or    If you had a stack of nuggets it converted it to how ever many gold bars it would equal too.  It doesnt have to be 4 stacks of string you could have 1 stack of string and it made it 16 wool. Etc  Just an idea.