Came across this thread while looking for a Bully MP mod - I'm surprised one dosen't exist by now! Then I got to thinking:
a Bully multiplayer mod (partially) already exists. Just use MTA:SA.
MTA:SA has all the features needed to import all the content from the game into the SA engine (same file formats, from what I've heard) with multiplayer support, simply using the
engine functions available in it's Lua scripting system. I have quite a bit of experience developing gamemodes and resources for MTA:SA, and working on a Bully server would be a project I would gladly help with.
Keep in mind, I haven't thought all of this through just yet, but from what I can gather so far it should be as simple as importing all of the models/textures (animation support in MTA isn't working properly at the moment) into the game and then recreating the gameplay via a series of MTA resources. This is a much easier approach than trying to reverse-engineer the game.
As a proof of concept,
here is a video showcasing a resource for MTA that added Vice City to the map.
[insert obligatory MTA > SAMP rant here]