Would you donate if those ranks were implemented? What benefits would they have? I can't image many people will donate money for new ranks if they ever get implemented unless there's some special perks.
That's the point...making perks.
Perhaps for highest rank, implement a "trusted marketplace" of some sort, ability to leave a +5 trust as opposed to +1...the ability to leave -5 rep as opposed to simple -1 rep and so forth. There are many features that can be implemented with ease.
Hmmm, that could be also abused. Just give some BTC, give negative trust to everyone