Meh, I don't trust a large "user-owned cooperative" much more than I trust Google. Then incentives of the owners may be more aligned, but the incentives of the people who actually run it aren't. For an example, see the collapse of the Spanish banking system, much of which was composed of mutual banks.

I'd trust a small cooperative, but then you still have the problem of federating between those, which brings you back to square one.