Yes, this has been done before with Winmugen. Perhaps this Ghidra program offers better results, but as you can see (other than the strings) every single function is labeled with a generic name which offers zero context as to their purpose or use.

You would need a person which is not only completely well-versed in CNS, but also patient enough to painstakingly go through every function and try to interpret its purpose. A person with such skills (and free time) would probably choose to tackle other projects instead.

For elementary uses, you might be able to to do easy things, like modifying game-modes to be simul-only or teams-only or very silly patches. Perhaps a more useful proof of concept would be to patch the hitdef code to accept integer numbers as attributes instead of just strings, this way you would be able to use triggers such as "cond" to modify their behavior.