Local Multicast Deployment
To minimize network complexity, would it be possible to "unicast" an image to a single master computer on a subnet, and have that master broadcast to remainder of the clients on that subnet?
This sort of already works this way. You can setup a new com server in that other subnet, the image is uploaded to it, and then it can multicast in that subnet from that com server. May not be exactly what you are thinking, but accomplishes the same goal.
Honestly I really like this idea, I used to do this with TRK (Trinity Rescue Kit), make a master machine, then use TRK to make a temp PXE boot, make the fresh machine the master, then it cloned it's drive to the other in the mcast session. Worked pretty good until EFI cam around.