No, you do not have to. Without embed all of initramfs is copied to the newly created tmpfs, including the stuff under
/opt/tce.
Another possibility which I have not explored yet, only read about in the syslinux manual, is if you use
any of the boot loaders in the syslinux/isolinux/extlinux family.
When you specifiy the initrd you could provide this as a comma separated list of (compressed or uncompressed) cpio archives. The resulting initramfs would then consist of the union of the contents of the listed files.
This should allow you to create one cpio with the stuff under /opt/tce and the other would be the
xxxxcore.gz originally supplied by MC/TC. This would avoid the need to merge your extensions into the
xxxxcore.gz files. In case you are using grub or any other boot loader this is not possible (to my knowledge)
/Lars