Cheers! We are developing an alternative web-interface for Steem blockchain - https://oneplace.media
We have started with feature #2 in your list (tag subscription, and we plan to introduce a lot of content filters as well) and we plan to implement #3. Feat. #1 seems a little bit tricky, e.g. if you would like to filter out the dominant language ("en") you would have to request a lot of posts from the blockchain before you find one post that is in your desired language, so a lot of time and load on Steem node. But I think we'll get to it at some time as well.
If you're interested you're welcome to follow our developments here - https://steemit.com/oneplace/@oneplace/oneplace-media-to-new-year-with-new-design-and-new-features