And then you can no longer deploy anywhere else, sounds perfect for the cloud provider!
I heard about that a few times already, but I never reached a point where my ecs setup combined with other aws services was not enough. If you had everything with just stuff in kubernetes wouldn’t it still be a pretty big deal to migrate?
And regarding Kubernetes migrations, once you've made sure you have network and DNS connectivity cross cluster it's essentially just replacing the CSI and LoadBalancer controller. Then the actual data migration there's no magic bullet, depends on what you run.
The USP for Kubernetes is that it's essentially the same no matter where you run it since everything conforms to the Kubernetes API spec.
If you don't want or need local development LARPing prod then anything goes.