I am strongly against (3) a private sale to investors, that will lose a lot of trust in the platform if influence is being sold through back channels.
Obviously some of should be (2) sold on exchanges to fund the development and marketing but too much of that makes me nervous - if the majority of trade volume on exchanges comes from steemit in the future that puts them in effective control of steem's price.
Burning (1) is something that creates trust and i'm rather indifferent to it.
Airdroping the existing Steem Power holders (4) in proportion to SP would make whales happy, but would just further consolidate power in fewer hands in my opinion.
(5) would be ok if there was a way to determine the best steemians. The only objectively deserving steemians i can think of are witnesses, and maybe they could use some of their stake to reward them, but not all of it.

My own suggestion is that they add a way of donating to the reward pool to the STEEM blockchain code if at all possible, add a special user like @null, but if you send steem to that user, it will be distributed as curation and author rewards. And then have them keep sending their stake to the reward pool.