For those wondering how this went: we had six participants, including myself. People had done their homework (or at least read the slides for the Diewald video), so we went straight for a discussion of things people enjoyed and didn't enjoy in larps, which generated a few interesting points.
After that, we talked about what larp we were going to write, and settled on a "Lord of the Rings bar". And so the Inn of the Clumsy Carthorse was born - somewhere near Bree, where Bilbo had stopped on the way home from his Adventure. We threw ideas at the board, wrote a character each, broke for lunch, then critiqued them. Which generated some more ideas, but as energy was flagging it was time to call it a day.
Currently the game is on Google Drive, and a couple of the authors have already been working on it. Hopefully we'll see it run sometime