I would agree that /opt is small enough to keep in mydata.tgz ... in my case. But someone who had something large in /opt or had an unusually pressing need to keep the back up -really- small might not find it so.
Also, some users might want to share personal data, but not, for instance, bootsync.sh and bootlocal.sh, among different machines. I do that, although I devised a way to keep boot*.sh specific to each PC.
In addition to the likelihood that it would be really really useful to at least -some- users, it seems to me that just the logical symmetry of being able to handle /opt and /home the same as the tce directory would make it worth updating the opt and home bootcode logic - unless there is some practical reason why it couldn't or shouldn't be done ( as there was a good reason not have persistent /usr ).