fetch+run extra rcS.d init script via livecd+dhcpcd

["Scott Edwards" <supadupa@gmail.com>]

I'd like to roll my own livecd (anything debian proper, or debian like
will do).  The one piece of my puzzle I'm still puzzled about is
allowing the cd to make a dhcp request I can distinguish as coming
from the livecd.  Based on that, I'd also like to offer an init script
(gpg signature thereof might be cool to) via tftp/http/https/ftp etc,
for the livecd to download.  I'm sure you can visualize as I do, that
anything is possible after that...  After the livecd is built, I can
update the initscript that'll be run after ip assignment on demand.

To give a little more background, there are about 20 workstations I'd
like to put to work on a task while employees are not on the clock.
They simply pop the cd in, reboot and walk away.  After they arrive,
they interrupt it and restart the system, removing the cd and work as
usual.

Is there a livecd that already offers something like this?

Thanks.