Well, I think I've read topics on multiplayer before. As far as I can remember, the only easy way to get multiplayer was to have both players on the same computer (ie. one using mouse and the other using the keyboard).
That said, that would be epic awesomeness to have a co-op campain. I don't know exactly how you'd do it, but if you can find a way to make it work, more power to you!
Good luck man. 
-If I were to implement this it would definitely require help from alec, and on top of that would have to probably make it a seperate element of the game.
Edit: Oh by the way [Edit #7] is up, a small glimps of yes, a blue "something". I most likely won't show the completed version of this VERY BIG boss. I spent approximately 6 hours working on it last night, and it's coming close to being finished.
RE-Edit: Now that I read this, it gave me but a small laugh. It actually took me over 12 hours to complete the boss the way I wanted it. But it is finished now. As with many other creatures not posted for obvious reasons as to not spoil too much.
