It seems simple to us because we're Wikimedians and we know what it means to edit Wikidata. Although the goal is simple, the solution will not be.

For example, we'll be making cross-domain requests (which adds potential for complications and performance problems), will probably have to interface with CentralAuth to check that the user has a global account (which we've never tried before and might not even be possible for the app), will have to work with Legal to ensure we're getting attribution correct (legally and ethically), will have to coordinate with Community Engagement to make sure that our editors are aware of the feature, and so on. If you want more details on all of this (because I could keep going if you're interested!), then let me know. :-)

Dan