Honestly I think this is an interesting an idea: not sure about the exact numbers that should be enforced, but linking your ability to earn as an author to the HP you own and to the HIVE you sold, seems more than reasonable and something that might help getting rid of quite a few extractors (or at least making their lifes harder).

Right now too many users use Hive just as a faucet, while we should build a system where users are encouraged to build up their HP.