Medieval/Shogun was coded in C/C++ using MSVC++ if I recall correctly. Unless any of our modders here are highly experienced with this, then they haven't much hope of doing anything with the source code. Editing a few .txt files is a whole different ballgame to coding.
I use C++ and have the source to another game most of which I can readily understand. Though there is a TON of code there, it's all broken down into parts, and you don't need to understand all of it to do anything with it. It's not like C++ is encrypted, unless of course the CA programmers were evil.

Still, of course, our chance of getting it any time in the forseeable future is ~0%.