Thanks for the questions.

• SP 파워다운 기간을 3일~7일로 단축할 의향이 있는가?
  (Are you willing to shorten the SP power-down period to three to seven days from current period? )

While shorter power-down period adds flexibility to investors so that they can get out sooner when needed, on the other hand, it adds uncertainty to decision making E.G. SPS voting thus may impact development.

IMO the system should find a balance to attract both short-term and long-term investors. Perhaps we could have 2 types of SP, one type is short-term which is for daily activities E.G. posting and post voting, the other is long-term which is for decision making E.G. witness and SPS voting.

• 스팀 블록체인의 다운보팅을 제거할 의향이 있는가?
  (Are you willing to remove down-voting policy of STEEM blockchain? )

"Gaming the reward pool" has always been a concern, that's why the down-voting feature is there. IMO down-voting should cost the voter something, because "stake talks". For example, my @adm account has been "donated" to @steemcleaners to fight bad contents since the very beginning of Steem, at my own cost.

• 스팀 블록체인에 스마트 컨트랙트를 도입할 의향이 있는가?
  (Are you willing to introduce smart contact into the STEEM block chain? )

Introducing smart contract is generally a good idea. However, there might be technical issues involved. On the other hand, although there are a few blockchains with smart contracts doing well, there are also quite some blockchains support smart contracts but nobody use them. The competition is hot. So, I'd say, if we have the resources (developers, funds and etc) and we can afford to lose the competition, we can do it. The key is to find our niche.

• 유료 구독 모델을 도입할 의향이 있는가?
  (Are you willing to introduce a paid subscription model?)

I'm not sure what does this mean. It seems a business on top of the chain to me, but not something to be built into the consensus. Generally we welcome all legit businesses.