So little time, so many plot bunnies, so many ways to get into a sticky mess. Though I get the feeling your list may mutate in interesting ways.

I agree that a collaboration would be hilarious. In the absence of messenger networks I've usually done it by...writing a page, mailing it, the other person writing a page, mailing it back. With however long between pages mutually decided. It does become very interesting, and the writing style usually becomes a compromise between the two.

It's immense fun...I thoroughly recommend it.