For brute-forcing registers e.g. in sd_uhs or LiveView (between x5 and x10 for uncropped preview).
Is it possible, only the knowledge and skills are required?
Pretty much. As long as the library is CPU-based, you can compile it (or implement whatever backend support that library requires*)), and the license of that library is compatible with ours, I don't see why it wouldn't work.
Lua is a good example of external software tweaked to run on the camera. I've also tried a few others, such as 8086 emulator (https://www.magiclantern.fm/forum/index.php?topic=14853.0) or hdparm (https://bitbucket.org/hudson/magic-lantern/branch/hdparm).
*) Here we may have a problem - ML is not exactly a POSIX environment. Turning it into one is certainly doable, but non-trivial. I actually wanted many times to do some steps in this direction, as the ability to run external programs (or adapt them with minimal effort) is going to be very useful.