A really helpful tool, would be the ability to transfer a domain from one account to another.
As a web developer, often I manage the hosting of a clients website, and as such I get them to delegate their nameservers to Cloudflare.
The problem is that when the client is no longer a client, but they want to remain with Cloudflare, its not possible to simply change the owner of the domain from my account to their new account.
Transferring would simply be a matter of changing the owner of the domain record, so that all DNS records, rules and settings could remain in place. No down time. No mess with transferring.