The plugin configuration would allow saving named SSH private keys specification of the path to the ssh-agent executable (standard scripting support to use a node attribute) and provide a configuration-wide Advanced Settings option to setup an SSH agent and a combobox to select the appropriate key.

Any step within the build which is the first step to run on a particular node during a build of the configuration will start the SSH agent process, add the key, and the QuickBuild agent will store the relevant ENV variables to be injected for steps run on that agent during that build. When the build is done the SSH agent will be terminated on each node used during the build.