Many approach charts are available for free and linked to by other apps as well.
It would already be a great feature to link to those free charts from within the app.
Maybe you could add something as a 'chart-link-build feature' so the community can help building the database with links?
This 'chart-link-build feature' should build a link from data supplied by the user and some fancy feature to automatically update the link with every new AIRAC release date.
... or something like that.