Someone higher up should enforce it. I've been in teams, where if something isn't in cloudformation it doesn't exist and that attitude is totally understandable, having to do some operations by hand seriously hurts IaC efforts.
Same with Config.
It may turn out that the tools that CloudFormation team provides don't make integration easy, especially if the operation takes longer than 15 minutes (meaning they can't implement support via a single lambda invocation as an under-the-hood custom resource).
But it’s hard to believe if the team responsible for the blue green deployment functionality developed an API endpoint to do it, they couldn’t just hand it to the CF team to call. At the end of the day that’s all CF does. Call APIs based on the different lifestyle events as far as how it actually creates resources.
Intentional or not, I'm going to start using this. :P