The easiest thing to do is put LILO and a kernel on the DOC. Configure the kernel for BOOTP startup, and NFS-mounted root. Then that's all you need! No root, no configuration, and like mhoyt said, all the tedious configuration and maint is done on the network server. Only the kernel updates need to go back to the DOC.
You could also put DOS on the DOC, and use loadlin to start up the same kernel. This way you don't have to tweak with (p)LILO, and you can still mount the DOC from Linux to update the kernel. I like that idea the best.
I have something similar set up to boot a diskless iOpener. Works great!
Debian's "diskless" package is a little too client-specific, in that it has writable mounted directory copies for everything. It makes it harder to maintain a fleet of these. LTSP goes to the other extreme and mounts *everything* read-only, with almost no per-machine configuration or non-volatile storage. I started with LTSP, and modified the startup to have a writable /dev and /var directory. Plenty of ways to skin a cat. Try them all!
