ye can't do it
It's like trying to add Multiplayer to Morrowind, ye might get a Lan campaign up working which has a max of two players who are unsync'd and most of all buggy.
Now, i'm no rocket scientist, but i would dare say that to be able to even create something close to this, it would be easier to create your own engine, your own game for that matter. If your team-mates are as skilled as ye so proudly claim, then what are they doing here modding a newly released game instead of working on a real game in the industry?