Honestly.. Hive inflation should really just be calculated from actual circulating supply only aka the first option.

I don't even understand why we're adding HBD into the equation when really HIVE and HBD should be entirely separate beside the conversion functions being the only link.

Inflation would then at least be predictable (Except for the fact HBD conversions to hive are inflationary which would be the only way they become inflationary in fact).
We won't have any issues with inflation running rampant due to HBD when at low prices at all then.