Thanks, gerald_clark, for your offer to reconsider the sequencing in the boot configuration. I was looking for quick and easy access to a setup that is as minimal on the server side as TC is on the client. I'm just embarking on a little project where -- eventually -- a carefully remastered initrd will make the nfs connection obsolete, so I was hoping to get by without running additional services.
Knowing that the current situation is a deliberate consequence of careful design makes me willing to live with it. (But if the design turns out to be improvable, let's do that.)
curaga's comments inspired me to make my own tcz-extension containing my tcz-acquiring and tce-loading commands, and then loading *that* by tftp. I put all those commands into a replacement copy of /opt/bootsync.sh, hoping the new version would be in position by the time the initscript had to execute it. Alas, I had a learning experience instead of a success: the unsquashfs command apparently refuses to overwrite a file that already exists. (And this is clearly a Good Thing!)
Deep into esoteric thinking now, I wonder if there would be any good reason for a boot option that directs TC to use *tp to go get a list of commands that should be run as root just before the setup process calls bootsync.sh. (You could generalize to insert such *tp-enabled hooks at various stages in the process; an early one could provide a versatile alternative to the nfs-initializer now in place.) Just a thought.
Thanks for your comments.