I see where you're coming from here, but I think it's a bit optimistic. By the time enough "extra" SBD has been printed to drive the price of SBD below $1, the debt load will already be in haircut territory. The change you've implemented increases SBD production when the debt load is already high relative to the 10% threshold. The debt load is very sensitive to STEEM price fluctuations... I think this change will add significant systemic risk.
Please note that it's really the haircut itself that I find objectionable. Your change is only problematic because the haircut exists.