If my understanding is correct, paying fees other than short fees out as interest should break the peg. In an uncertain market in which demand due assets matches demand to short, the peg should work. If everyone wants to short, that breaks the peg, which is why we had to use the price feeds. Allowing the shorts to pay the longs interest should recreate the balanced/uncertain market in which the peg works, but providing additional interest from other fees to asset holders would then break the peg again by increasing demand for assets.