I would much prefer having the option to tie Item Banks to courses instead of instructors so that this didn't happen in the first place, but just in case this is quicker/easier (or in case Canvas never does get around to implementing that feature), it would be extremely helpful if people who are "unauthorized" to edit Item Banks could request access.
As an example, I'm helping run a sharing site for a group of TAs. I had to bank the questions in a quiz because I wanted to export them to a different course; this is the only way to do this in Quizzes.Next. That also closed off the quiz questions to the other TAs; when they try to edit them, they get an error message saying they're not authorized. I know I can give them authorization by sharing, but I wish there were a way for them to ask for authorization—within Canvas, not by using external means. If someone were to bank an item and I had no idea who, it would take much longer to find out by emailing everyone in the course than by being able to hit a button in Canvas that sends the bank owner a notification that someone is requesting access.
Again, it would be even better if this problem could be eliminated entirely by allowing Item Banks to be tied to courses, but if there's any chance that won't happen, this would be the next best thing.