My bad, I was in part replying to the previous post about doing it in bootlocal.sh on x86, in my case it was x86(8.0) not Pi. But that said tce-load does do '[ -d "$TCEDIR" ] || exit 1' so I'd assume it fails on all platforms once you've unmounted the device tcedir points to.
I've just noted though that in the code there's a '-t tcedir' option not mentioned in the usage text which seems a more reliable way of scripting subsequent RAM based loads once the boot media has been removed, without having to fix the symlink.
I'm new to TCL even on x86, but do have an unused RasPi 1 without an SD card. This topic has kind of piqued my interest generally, I think I'll order a new memory card and give piCore a whirl too.