By any means? Is there a little mod that converts hotseat into mpc? Saw something like that for Kingdoms.
I made an app a while back that simplified the file transfer over a LAN via a shared directory, but that's the closest I know of...
Edit: Here. You can ignore the spoiler window unless you don't trust the files I attached and prefer to make your own files. It works in conjunction with quicksave files, but you could edit it to transfer any file. It's just easy to hit ctrl-S, then tab to the app window and press S in it again... presto, your quicksave is now on the network drive. Whoever else is playing does the reverse: they press L in the app, then tab to game, ctrl-L and are all set up. Just make sure to map the shared directory and set rights so people can write to it.
Yeah, CA is betatesting a MP campaign for ETW but its only 2 human players vs AI. So not likely we'll see a modded multiplayer campaign for M2TW if even ETW is that limited.