If we could establish a free lending and borrowing market in BitUSD, where borrowers pay interest to lenders, I am very confident that BitUSD longs could then earn much higher rates of interest than this by lending it out when not needed (initially the borrowers would be selling to go short, which although more costly than opening a short directly on BitUSD, is less difficult and has fewer restrictions). I think this would increase demand and confidence in a rate of return generated internally in the market without the need for subsidies.
I now think of BitUSD as like cash in hand. It should not have to earn interest if used for facilitating payments. But as a potentially longer term store of value, I want to be able to 'deposit' my funds and be compensated by those who would like to use the BitUSD.