In our current kick infrastructure the 'default' pxelinux file loads a staging environment that determines what os to build the system as and created the initial pxelinux file. Once kicked the system specific pxelinux file boots to the hd. Foreman has no current support for a pxelinux file for systems not currently undergoing a build, however for true unattended bare metal provisioning this is a requirement.

The stages would be:
bare system -> boots 'default' to register with build system
registered system -> boots build defined in system registry
built system -> boots hd

I can't have the default boot to hd, as then new systems would not be provisioned because I cannot add the tftp file for the new systems before hand as I do not know their information until they register.

Having an option for foreman to rewrite a second tftp template for a system once built would be better than just having it delete it entirely.