Sure then throw Ansible over the top for configuration/change management. Packer gives you a solid base for repeatable deployments. Their model was to ensure that data stays within the VM which a deployed AMI made from Packer would suit the bill quite nicely. If they need to do per client configuration then ansible or even AWS SSM could fit the bill there once EC2 instance is deployed.

For data sustainment if they need to upgrade / replace VMs, have a secondary EBS (volume) mounted which solely stores persistent data for the account.