The add-on anki remote decks brings a lot of this functionality already

This suggestion should be split into two:

• Allow users to subscribe to a shared deck, with notifications each time it updates (and perhaps even auto downloading as a configurable option).
• Improve the deck importing functionality generally:
• Improved updating of existing cards (sometimes it fails as it finds no difference, when a difference exists)
• Ability to Reset a note/card's progress (if the information is now completely different)
• Ability to Remove a note/card (if the info is no longer true).
• Option to not move the cards if they already exist, rather than a deck being created each time and moving all the cards to there.
• Same choose your own field mapping when importing an ankideck that you get when importing a csv. Sometimes I wish to say "do not overwrite field X" or "map X to Y" but cannot unless it is a csv.
• All the above being at least a warning to the user before it happens of course, with their full control to allow or disallow. Nothing should be deleted, reset, moved, or changed without the user being aware.

Having these features in Anki proper would be a godsend.

The special fields add-on is currently being updated so that it will be much more friendly. Also check out medicflashcards.com which is intended to do what you are saying