Shaun_Max Is this something we can do by ourselves?
Not easily. As you've discovered one of the key features of it is it works on the binary data to make the code impossible to compile. So the normal hacker approach of decompiling, making a few changes, and recompiling it won't work.
To do this you need a deep understanding of the Flash binary format, so you can modify it in ways that break decompilation but which do not stop the code running.
Other things you can do yourself, such as renaming all variables, classes and methods. If you do this across all source files you can do a much more thorough job of it. Numbers and strings can be hidden in some way: encoded or looked up in binary data. None of this stops a determined hacker but it can slow them down and deter casual hacking.