I would like to see account numbers be portable like phone numbers are now.
You can bet the banks didn't think of this themselves, but it was probably forced on them by a consumer protection law. It is, coincidentally, something most Dutch people don't know exists.
Can you explain your reasoning?
Often with things like auto-bill-pay, you have to wait a billing cycle for the new changes to take effect. And you generally have to keep the two accounts open until everything is switched over, or face the wrath of failed direct debits.