Good idea Werner, thanks for the suggestion!

Here is my detailed explanation for novices, and a working code sample (tested on v6.7.1dvd), for those who wish to use this method:

knoppix.sh is executed during startup by a block of code that can be seen at the end of /etc/init.d/knoppix-autoconfig. If one wishes to undertake a deep remastering, it is possible to modify this code to build a script-inhibiting cheatcode into the system.

Alternatively, a conditional code block can be inserted at the start of knoppix.sh to parse /proc/cmdline, the kernel boot instructions, for a specified keyword, for example no_myscript. Use this keyword as you would a cheatcode, by typing knoppix no_myscript at the boot prompt, and the code shown below will suspend script execution; if the keyword is not entered, the script will execute as per normal.

Code:
string=$(cat /proc/cmdline);   # Assign output of 'cat' to variable 'string'.
   
if [ "$string" != "${string/no_myscript}" ]; then   # Check for presence of keyword.
   echo "Stopping Script"
   exit
else
   echo "Running Script"
fi
Note that knoppix.sh is not executed in Bash, but in a Bourne shell, so some more common Bash commands that check whether a variable contains certain text will not work properly; for instance, grep will not work, nor will [[ "$string" == *no_myscript* ]]. Hence my use of the clever method published by one ephemient on a thread at stackoverflow, and described by him as follows:

${var/search/replace} is $var with the first instance of search replaced by replace, if it's found (it doesn't change $var). If you try to replace [no_myscript] by nothing, and the string has changed, then obviously [no_myscript] was found.