Adding a session including the files from original session and some new files should not be difficult.
Only thing is to stop all writing/reading to/from CD except the burning-software while burning new session. This could be done easyer if you shut down X-server and close all shells (e.g. go to lower runlevel).
After burning, it is NOT necessary to update ramdisc, links ,... !!!
Only reboot and knoppix runs customized !!!

So what do you think, could this recipe work?

1. Goto runlevel 1
2. Create compressed homedir/settings-files to extra ramdisk/folder
3. Copy all needed programs to extra ramdisk/folder
4. Unmount cd
5. Burn new session to the cd
6. Reboot