With regards to point 3, Steemit has fixed that with posting limits of 4 in 24 hours. Anything after that will be punished. Edits also count as new posts. You could end up earning $1000 on your post with a payout of $100 based on posting/editing too much, more than the allowed in 24 hours. Very good points. A posting fee would off-put a lot of people though. I don't think that should be done in my opinion.