Although I have to point out that the proposed change to the code by @blocktrades that will allow conversions from hive to hbd will introduce a key component to the tokenomics that will balance out the negative side effects of hbd conversions.

I imagine you are referring to here to reducing HIVE in circulation by turning it into HBD (alternately, moving HIVE from available supply to virtual supply), but the fee aspect of the proposal is also interesting, since it represents a permanent burn. The existing conversion (HBD->HIVE) doesn't have a fee, but I would ultimately like to see the fee applied in both directions. This probably won't be done initially to minimize the complexity of the implementation.