In some cases hardware or VMs which cannot be included as part of the foreman life cycle management because of lack of one component such as TFTP or compute resource API.

A method to (re)provision a host could be considered where foreman can be provided with an IP/hostname along with SSH key/password to complete a (re)provision of a host by foreman. Example, http://blog.theforeman.org/2012/01/re-provision-host-without-pxeboot.html