Mmm, yeah, I was thinking of using multisignature BTC addresses to do the escrow, but probably an escrow service is easier.

But it's hard to prove you have sent an anonymous currency, no?  So you need the lender to be honest to the escrow service.
That's why I wanted to lender to put in a small amount in escrow as well, so he has an incentive to be honest to the escrow service that I sent back the DRK.   

Pfft, looks like this might be too hard to pull off.