Hey,
Though an “expand and contract” migration like you’re thinking is a common tactic here, it’s more commonly used on-prem and not so much for straddling VMs and K8s.
While there’s nothing stopping it working in theory, the suggestion was that using mongomirror would be a viable, likely simpler, alternative than trying to create a replica set that spans k8s and VMs, managed by the operator. Cluster-to-cluster/mongosync if you’re on 6.0+
Worth noting that neither is an official option here. Mongomirror is not officially support for a self-hosted to self-hosted migration, but does work. And there’s no official support for Community when it comes to cluster-to-cluster https://www.mongodb.com/docs/cluster-to-cluster-sync/current/reference/limitations/#mongodb-community-edition.