Ok, the next thing I just tried and tested is to check where the files get stored. And good news is that addition/subtraction within a jail gets replicated to the main filesystem where the jail is stored. So if you add a test.txt to your node (jail) in /root, that file will appear in /usr/jails/node/root under the host OS's filesystem.
Knowing this, I thought I could directly PXE-boot from a jail by NFS-exporting the /usr/jails but unfortunately the jails do not have any "kernel" to boot from?!! And an NFS mount cannot see the contents of the basejail and boot directories (/usr/jails/node/basejail and /usr/jails/node/boot).
Any ideas how to fix this?
Thanks,
atwinix