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

Good option as the trouble of locking funds indefinitely can be addressed. May need to change or investigate the post payouts economics to decide the exact number of days IMHO.

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

Agree to @netuoso

Are you willing to introduce smart contact into the STEEM block chain?

Absolutely and the options explored by DanL should be investigated. There were discussions regarding Smart Contracts in the past. There was some work using a programming language called WREN also was done. Refer : https://steemit.com/blockchain/@dantheman/a-better-approach-to-turing-complete-smart-contracts

Are you willing to introduce a paid subscription model?

More details will be needed. That being said, attempts to make the chain self-sustainable without coin sales like what was going on will be great. There should be sustainable mechanisms to create revenue. Any reasonable means to achieve is welcome.