I gave this a little more thought after my initial response last night.

4 - If the price is below LOW, use the HBD to convert into HIVE (takes 3.5 days). Upon completion of the conversion, use the HIVE to buy HBD and send that back to the DHF

One of the reasons I would support this would be to limit the printing of HIVE, particularly through HBD conversions. After the conversion is run, instead of sending all HIVE back to the DAO, could a portion be nulled? This could push some value into HIVE rather than creating more inflationary pressure.

If this system is then combined with an HBD "DeFi" solution that's paying out yields for holding HBD (maybe only to those who hold HBD in their savings account), then both HBD and HIVE would gain tremendous value over where they are today. Yields earned from holding HBD would also help keep at least some downward pressure on HBD prices as holders sell off those returns, so there's a little less risk of runaway prices.

The interest on HBDs, if only paid to that amount held in savings, would also limit how much would be going to exchanges that hold the tokens. On the other hand, some exchanges may want to list HBD as a "DeFi" option where customers can essentially stake HBD on their exchanges for a share of the interest payments. This brings more visibility to Hive and additional listings/pairings would help with exposure to and liquidity for HBD, which is sorely needed.