OP, I'm not sure if you're aware of bitmex.com? They run a 'fixed' version of bitUSD on their centralised exchange where both shorts AND longs pay/receive interest based on the deviation of the price from the peg.

Essentially, a 1x leverage short on bitmex is a bitUSD equivalent.

I know this cannot feature in your list of decentralised coins, because its neither decentralised, nor a coin, but for purely academic purposes I find this very interesting indeed.