Bankchains solve #1 by not using mining; they use something like BFT (which is basically Paxos for liars) so that only 51% of the companies in the consortium need to be honest at any one time.
Ah, I forgot to mention that. Bitcoin is totally trustless, while bankchains require the participants to trust each other's identities but not their behavior. Whether this trust model is applicable in any real-world situation is debatable.
And yes, if you're using blockchain to track something like gold in a vault you might as well just have a database that is run by the same entity that runs the vault.