It would be exploitable. If it becomes more profitable to stay in powerdown and move the HP from account to account, people will actually do that.

This has been a question since the very beginning and (believe it or not) you are not the first one to make such a suggestion. Honestly, it is kind of stupid, like sun's idea to make the powerdown period shorter than the posting reward window. It makes no sense and doesn't fkn work. (lol)