Bumping this thread. I was trying to parse the code for LibreCoop recently, the multiplayer coop mod for Doom3, or Dhewm3 more exactly. The main alternative is OpenCoop, but I think LibreCoop is more developed. Anyway, it got me thinking how much work would have to go into a coop mod for TDM. It's still my biggest wish item.
The idea I got was one has to basically walk system by system through the code and think about the client and server side of packet swapping. TDM has a lot more and more complicated systems than Doom3, but once you start getting a feel for it, I think the basic system doesn't change that much. In a way it reminded me a bit of a pared down save/load system, what you need to update a game state, except you're streaming it in in real game-time, and you using tricks to fill in gaps to ease the load.
The other thing I noticed is that maps themselves need their scripts tweaked and anything else happening in the world. But I wonder if there's a way to procedurally do that when a map is loading, so one could just use the FM files as released.
It looks like it'd take more than a year or two if one were working steadily through it, although I think one would get efficient at it over time. Like I was noticing, there's a consistent logic to it. But most of all I think it'd be worth it. I really like Thief coop, and I think it'd be great for TDM. I'm just FYI'ing about it now because I was browsing through the other coop mods. Not even soliciting opinions or anything. Just thinking aloud (avisible?) about it.