Allow people to buy and sell donations in other peoples names. By adding tradeble credit tickets. In $10,20,30,50,100 or whatever numbers look right. (or whatever system for buying / selling donations would work best)
These things bought would not add to the total donated on your account, but would be able to be claimed to give you the donation total + the points you would normally get from donating.
This way people would be able to "buy" donations to get rdi and ldi on their accounts.
It would also be a big donation incentive because people would love to spend good amounts of money to achieve those ranks.
Which when the price is right, people love to donate to make a big gains from donating