(Are you willing to shorten the SP power-down period to three to seven days from current period? )

A few days power down is too short and opens the door for vote abuse on rewards: vote, powerdown, powerup/delegate to another account, revote. This is unacceptable. The minimum should be >7 days (past the reward payout). Also, short powerdowns allow hackers/phishers to steal funds very fast before account recovery is processed. The power down has been extensively discussed and I'm in favor of a 4 week period, it's a good compromise especially for security reasons.

(Are you willing to remove down-voting policy of STEEM blockchain? )

The downvotes were designed to prevent abuse, otherwise it would be a wild west for circle jerking and reward milking. However as mentioned by @netuoso, with the upcoming SMT's you can control downvotes and exclude bad users are you please.

(Are you willing to introduce smart contract into the STEEM block chain? )

Sure, why not, adding technology to the STEEM blockchain is always welcomed. It may require a lot of development (look at SMT's... we're still waiting for them after 3 years of promises).

(Are you willing to introduce a paid subscription model?)

You can have your own model right now without any additional blockchain development. By creating accounts for users yourself and giving the private posting and active keys to your subscribers, while retaining the master password and owner key. After the subscription expires, you change the password, which will consequently change all the private keys. If the user renews subscription, you give them the new posting/active key. And finally, with communities, you can grant the users access to them or not. The current system is very flexible as you can see, and readily allows a custom tailored subscription model.

I hope I answered all your concerns. I'm witness @drakos and your vote would be appreciated, especially in this troubled time. Thank you.