The only realistic way to do this would be to go into multiplayer mode on a server, send a live image of the game to the client player, and get control input from that player. That's basically what remote desktop is doing.
But have you seen how much CC lags while you're getting images of it? You're going to need a supercomputer to process all of that. This is why there isn't going to be live-action multiplayer. Sorry folks.

Actually TLB, I am not familiar with this terrible lag. I even managed to make the game display on a wireless G connected laptop, hosted from the main computer.
The trick was getting it to only send one section of the screen, which decreased the network load considerably.
The host was a ~2.8 ghz dual core iMac of something around a year ago, the laptop was an iBook G4 of a million years ago.

I figure with processing capacity advancing so well nowadays, it would not be out of the question to use a screen-diving tool to control who sees what, by creating VNC connections for each non-P1 player. The performance would be directly proportionate to your network, but that too is not difficult to upgrade. I dare say games in the past have made more aggressive hardware demands from customers.
That said, CC does not need yet another thing to suck out CPU cycles, it does that fine all by itself.

If I remember what it was that made it work so well I'll post a mac tutorial or something.

P.S.
Your avatar still surprises me, what feels like years into my-seeing-your-use-of-it.

Please do. I'd rather like to see how you did it.

That could do it, yeah. There's still the problem of distance between computers and latency, though.

My testing on a great connection returned success, but it was pretty mediocre and the resolution had to be quite low (technically this was the normal CC resolution of 640*480).
It's nothing like practical yet for online play, as any sort of latency results in something unplayable.

Maybe in a few years, when more areas in the US (and elsewhere) roll out infrastructure upgrades.
Until then, it's a lan-only kind of thing, and less reliable than an IR link.