IMO, this post shows that you're starting to learn a bit about the ecosystem that you have entered, so I'm glad about that!  It's more than just blockchain, and it's more than just social media.  The two interact in a unique way.  And you're still only scratching the surface.  Please continue.  I know it hasn't seemed very welcoming, but if you persevere, I am sure you'll see that there's still sooo much unrealized potential for Steemit in this ecosystem. 

Although I don't run a witness, I'll respond to your questions: 

I don't agree with 3-7 day powerdown because (i) it could enable people to get curation rewards twice with the same Steem; and (ii) it would weaken security by enabling hackers to power down their victims' accounts before the account recovery mechanism could be engaged.

If you're serious about removing downvotes, I'd suggest coupling that with a rewards mechanism that's modeled after a [second price auction](http://www.gametheory.net/dictionary/auctions/secondpriceauction.html) in order to discourage overvalued rewards.  I'd also suggest finding a way to try it out with an SMT before deploying it on the base chain.  I wrote about the 2nd price auction, [here](/@remlaps/simulating-a-steem-curation-rewards-distribution-that-is-modeled-after-a-2nd-price-auction).

A second price auction may be an improvement [because](http://www.gametheory.net/dictionary/auctions/secondpriceauction.html):
> The theoretical nicety of second price auctions, first pointed out by William Vickrey, is that bidding one's true value is a dominant strategy.

There's no need for downvotes if natural incentives encourage people to avoid over-bidding.

With the current algorithm, however,I think downvotes may be necessary (although abusive downvoting is a very real problem here, and it's not clear to me whether the cost outweighs the benefit).

FWIW, I am strongly in favor of private property, raising the value of Steem, and welcoming investors & exchanges.

Please continue to interact with the community like this.  I honestly think it can benefit Steemit's bottom line and the Steem blockchain to have you engaged here!