-EDIT-
For Collateral, does the Borrower also need to provide the 3% interest along with the original loan amount requested? So totaling 103% btc Collateral?
I am willing to provide more collateral than the DRK are worth.
For security of both parties; With the Collateral your using DRK, I'm thinking an escrow service can accept both DRK and BTC from both parties, then confirm and release the DRK to you once each party has funded escrow.
Also keep in mind about escrow fees. I'm not sure on what kinda percentage fee your looking at for them securing your collateral for 1month...