We use a separate VPC per environment. Does or will spinnaker support targeting different Kubernetes clusters? Will adding environments ad-hoc be viable?
Spinnaker supports multiple Kubernetes clusters, each is added as an 'account' in Spinnaker configuration. The configured accounts are presented as options at deployment time, and the Server Groups for each application are rolled up under the account they belong to.
It is possible to change that configuration and refresh it at runtime, but it would involve editing the on-disk yaml file that backs the Clouddriver component of Spinnaker and triggering the /config-refresh endpoint.