If I'm not mistaken, the orginal cab has to be linked up with others for the mulitple play option. (for simultainous play.)
This wouldn't necesarily be what Kaillera does.
I would think that MAME would need to emulate that component of the linking hadware interface along with a simluated way to let 2 independent PCs link up and comunicate through it as each PC runs its own version of the game.
Each player has its own view, etc, which differs from Kaillera putting each player in the same place and the same time, with the same view.
My 2 cents.
Smack