WARNING!!! this is not workable yet, hopfully soon.
These plugins give subcontractor the ability to do things. Which plugins depend on network access, network permissions, and design coderations. For example, the network that has access to the IPMI's of the baremetal servers probably does not also have access to vCenter. So a instance in the vCenter network would have the vcenter plugin and iputils (for ping/socket tests of the installed vms) and another instance in the out of band managment network would have the IPMI and iputils (for ping testing the IPMI interfaces). This way network segmentation can be maintained. Each instance will need HTTP(s) which can be proxied back to contractor.