In a way, we already do a little of this here on the community.
The problem giffgaff had when I was with them was that they relied solely on the community with agents practically refusing to provide any support that wasn’t a small set of account specific queries. When people were heavily incentivised to reply to questions and have their answers accepted, I found I was left with low quality, irrelevant replies to technical and service questions.
I think a good balance is to have multiple tiers of support, starting with self-serve resolutions and information on simple or common issues. This includes showing declines with reasons in the app, status information at the top for outages or degraded performance of the service as well as card freezing and replacements due to loss or damage. Then the community forums for specific issues that affect a wide range of people or general discussion of upcoming/new features. Finally, the layers of “real” support for fraud or account issues ranging from email, private messages on social media and in-app chat to the emergency phone number.