The crash cart is the method of last resort, and it's come into play a fair amount as we were figuring out how to do this.

The better solution is to have a NetRestore server on the network, and configure the Macs to boot from a particular server with the bless and nvram commands. Then on the server, you control if the image gets served or not based on some external logic (in my case, an attribute in my machine database).

At the moment, NetRestore is running on an OS X Server machine hanging out on the network, but integrating it with our existing Linux netboot environment is on my to-do list.

Have you considered a thin-imaging solution like DeployStudio?

I think our solution is pretty similar in concept. We just deploy the base OS (with enough config done to ssh in later) via NetRestore. Then whatever packages or setup tasks are required is done in a post-install step using Ansible.