Live Migrate through VPC peering connections
Many teams put their databases in subnets without internet access or with just a NAT gateway. It would be great if the Live Migrate could be use through already configured VPC peering connections.
Have you looked at running mongomirror yourself? This gives you the ability to "push" the data from your VPC to Atlas, and mongomirror is what powers Live Migration. For completeness, this model works for replica sets but not sharded clusters. https://docs.atlas.mongodb.com/import/mongomirror/