Hi all, I think it is necessary to support heterogeneous invoker cluster. For example, users might need GPU enabled host, and users might expect more powerful hosts or dedicated resources with higher prices. Or OW operator(public cloud) might want to deploy invoker in many different types of host machines to maximize the utilization of computing resources in the cloud. And the heterogenous invoker cluster requires heterogenous prewarm configuration for efficiency and flexbility as well. And i writed a issue here: https://github.com/apache/incubator-openwhisk/issues/4240
