I have already written a script that takes your existing tce directory and creates an opt_tce.gz out of the contents and creates an iso based on an already downloaded release iso. In other words, be running TC, mount install your favorite apps through the appbrowser, download a release iso, then run the script and it spits out a premade iso with those extensions integrated in /opt/tce. A warning message appears indicating the RAM the extensions will occupy not counting run time use.
I used the method mentioned by danielbarnes that keeps the opt_tce initrd seperate so it is easy to just copy that file and the isolinux.cfg from one release to another. I may consider putting a GUI to this, maybe Xdialog, but that is really not needed as there is only one step involved and that is choosing the base iso you want to start with. After some more testing I may post in the programming and scripting section.
I may add an option to include your backup as well if /opt/tce supports it so the cd could be fairly personalized. While providing a prebuilt desktop is not what TC is about, I know there are times when a preinstalled cd is desired. I was using a Windows machine away from home for a while where I had no Linux access to the hard drive and the usb ports were no longer working. I got tired of redownloading all the extensions I normally use as well as having no saved settings, so I made a cd a while back. It made life easier, and I think a tool to make it easy to make a custom iso would be practical for those who want it.