Cool feature set, but this definitely doesn't deserve 28k. And not over a period of a year. I would suggest that you break this proposal into sub proposals, each proposal being one of the big features. like "mobile steemworld", "sds", "interactive post editor".

This way people can support what they want to support. I am down for the sds part. I don't care about the steemworld parts. Thus I won't be in favor of your proposal because I know that some of the funding will go to things I don't want/care about.

Also I don't think the sps should be used to fund closed source projects (like steemworld, correct me if I'm wrong).

Tl;dr : the sds is a great use case for the sps, the rest not so much.