I wonder if at boot time, with tcelocal= variable set (or whatever is it named), one could also specify tceload=file-without-path.tce
That way, i18n and L10n, customization, branding and whatever could be accomplished by simply adding a directory and editing a syslinux.cfg/ isolinux.cfg simple line.
If that data/config/dummy .tce have an associated .dep, it could also install some other .tce's at boot time.