SP 파워다운 기간을 3일~7일로 단축할 의향이 있는가?

I'm not negating shortening power down period, but there are serious security implications (as you can see in current case - exchanges were willing to abuse funds just because they were promised to PowerDown fast). Such "light" stake should be restricted when it comes to impact on governance.
One of many potential solutions was presented some time ago by Steemit Inc., but recent events caused their leading blockchain developer to resign.

스팀 블록체인의 다운보팅을 제거할 의향이 있는가?

Votes whether up and down are integral part of Steem, i.e. e-Steem-ation of content via so called proof of brain (but sometimes lack of there of). I'm happy to see SMTs that combined with communities can figure out their own reward distribution models that would include no downvotes if a given community desires so.

스팀 블록체인에 스마트 컨트랙트를 도입할 의향이 있는가?

Steem itself isn't designed for smart contract, but it's possible to use similar solution to a middle-ground blockchain for compiled code and smart contracts that one of our witnesses developed to enable it for BitShares users.

유료 구독 모델을 도입할 의향이 있는가?

I don't know what you mean by that but I beleive that's something UI based that's up to service providers. Steem transactions are free.

Please note that the witnesses are not really someone who make decisions. Witnesses are servants of the platform providing security and reliability to serives, like in every DPoS system there are stake holders who vote accordingly to their desired way of how Steem should look like.

These days there's also Steem.DAO that can be used to vote for desired changes and implementations and their funding.

Thank you for voting responsibly and at least not allowing centralized entity to override governance of the platform.