I was considering implementation of bond idea only because everything is better than current system. Current one is horrible on technical level as well as the "correct interest rate" discussions are always political and emotional. If we are to have interest on HBD, the rate has to be subject to market forces, which would be possible with bonds. However if there is a better way to achieve the results I'm all for it. Devil is in the details though, so I'll wait for the opinion of someone with experience in the matter (I think BitShares had AMM implemented, no? @abit).