Keep in mind that the game is hardened against tampering, so any form of tweaking you’d like to do, E.G. Buffing the shit out of the Wraith; is nigh impossible. You’d need both the decryption key and the private signing key to get access to the files you need to “patch” and this is just the basic functionality (I.E. tweaking damage, traversal regen, etc). The decryption key to get to the files you need to modify, and the private key to re-encrypt them. The game doesn’t have a “directory” functionality, as far as I’m aware, so setting it up into a sub directory into the game’s folder won’t work.
The rest of the engine stuff, such as fixing the basic Gorgon bugs (the twitchy animations, the wall pounce bug, the mimic bug) are out of the question for instance, as the flaw is hardcoded as far as I’m aware.
I don’t know about net code, but it’d be hard to do imho. In other words, integrating a new set of software would be tough to do. You’d have to fiddle with memory addresses and injection into the game itself. That is a whole other can of worms, one I’m not familiar with.