A Polyamorous Ketubah?

I was talking to a friend about my polyamory post (next time, girl, can't you comment here!), and she asked a great question:

What would a polyamorous ketubah look like?

Obviously "k'dat Moshe v'Yisrael" would have to be modified but would the ketubah simply allow for further ketubot? Or perhaps it would have space to add more partners along the way.

What do you think? How could a ketubah be worded to support open relationships?