[Pulumi founder here] Sorry to hear you don't particularly like Pulumi---any/all feedback welcome. If nothing else, we do listen and we do try to get better. -Joe
$ pulumi config set numberOfAvailabilityZones 3
$ pulumi up
And Pulumi will compare the current infrastructure with the new goal state, show you the diff, and then let you deploy the minimal set of changes to bring the actual state in line with the new goal state. This works very much like Terraform, CloudFormation, Kubernetes, etc.