I don't agree with the minimum price formula. That means if all SD in existence right now except for 1 SD was collected into one account and then converted to STEEM with a single conversion request, that 1 remaining SD would likely be able to claim 13503 STEEM (which at current prices is worth approximately $19,444 USD) through a later conversion. Now obviously, that is a ridiculous example, but it demonstrates how a sudden large decrease in SD supply due to conversions, can cause later converters to get a lot more STEEM than they should due to that minimum rule, even if the price of STEEM in USD doesn't change.

There is no need for the minimum price. If the USD hyperinflates (which I disagree with you regarding it being more likely than the other type of black swan), then the witnesses could just transition to tracking the price of some other asset with reasonably stable value. For example, the witnesses could instead track the price of some other currency, or if necessary maybe even the price of gold. An appropriate factor would be included into the definition of the price being tracked so that there isn't a discontinuous change in the SD/STEEM feed price during the switch over from tracking USD to some other asset.

The social contract regarding the price feed should not be to track USD, but rather to track an asset with relatively stable purchasing power that has a well-defined computable price relative to STEEM, whichever the best asset for satisfying those conditions is at the time. Obviously, we would also want to avoid switching the assets we track unless it is truly necessary to satisfy that social contract. And the decision to switch and the particular asset to track instead should only be made after extensive community discussion (and enough time for stakeholders to reflect their views through witness vote changes) which includes the opinions of both relevant parties: SD holders and STEEM/SP holders.