Content-free can easy go with spam-free :)
But already now you see on Hive all kind of spam and account farming, so some form of penalizing needs to be there.
I agree that the earning cap would be the least radical of your suggestions. But would it bring that much? Same with forbidding autovoting. I write typically quite decent content which usually takes several hours work, why should I not be allowed to upvote it?
Anyway, if you want to keep Hive a minimal niche for a few nerds, that your suggestions would pave the way :)
RE: HOW TO MAKE HIVE A BETTER PLACE