I have no doubt that market consensus will make bitusd track the price of USD.
but the rules with leak will break the market consensus.
the rules with too many limit will stop the market consensus.
I think we should make a rule with less limit, and without leak.
here is my solution.
the main different is the short bitusd is separate from bid XTS.
for example:
If I want to short 100 bitUSD with price 1bitUSD/xts, I need to freeze 200 XTS, and I can get 100 bitUSD immediately.
then I can usd these bitUSD to buy XTS with a different price, for bit order. maybe 0.5 bitUSD/XTS or whatever, there is no limit for the price of bid order.
the same, there is no limit for the price of ask order. there is no limit for the market depth check.
the key is to limit the short price.
the maximum short price is coming from the minimum matched bid price of latest blocks(maybe latest 24*60*6 blocks).
at the beginning there is no matched bid price, we can set a safety initial limit price, come from the central trade market, like 0.01USD/XTS.