Good idea, I'll probably add a fourth filter on top of cargo to only show "useless" ingredients (i.e. ingredients that are not used in a single blueprint and ingredients that are only used in ignored blueprints) such that people can easily clean up their cargo.
Regarding the dataexport, it's something I plan to implement with a lightweight local server. You would use your browser
Code:
http://localhost:8083/Zach/materials.json
and you would get the content of your materials. Some more routes like cargo, data, commodities, blueprints, favorite blueprints etc... Could then easily be added. The idea is that the user would chose which format he wants (like json, csv or xml) so it could be consumed by anything. Local applications could poll these URL regularly to get an updated version of the cargo (EDEngineer taking care of tracking the logs, which is pretty error prone and took a while to become properly working).
That's a mid-long term goal though, don't expect that to be there so soon