The idea of 'supporting the value of steem dollars' against market forces is a bit like asking people to pay more taxes than they ought, just to support the good ol usa, be patriotic. If the 'value' of the steem dollar is less than the dollar, then it is so. Only by improving the value of what the steem dollar represents can the steem dollar increase its value relative to the dollar. In fact, there is no rationale for having any 'peg' or backing to the steem dollar other than what the steem dollar is good for by itself, such as spending it with people and businesses who want to receive it, and using it as a savings account, as it seems there is actually a real return, provided you wait to cash out at the lower 'dollar' valuation, or some other valuation depending on the alternate currency or commodity. Leave it up to the individual to decide what they wish to exchange their steem dollars for, so they can pick the one they like, whichever the best value is at the time, such as bitcoin, maybe.
If there were to be a 'peg', which is just an arbitrary thing anyway, as people can if they like sell the steem dollars for $0.01 each or less, then the 'peg' should be an average of the global currencies and metals, like gold & silver & copper & palladium & etc., and the 'dollar' and the 'yen' and the 'yuan' and the 'euro' and the 'pound' and so on. Average all those valuations, however the money magicians do it, and say your 'steem dollar' is worth that, which technically it is. But people can and always will choose to sell lower and buy higher, and vice-versa.