Does drop-in-drop-out work at ALL with a GM mode, though?
I don't think that it does - especially not for the GM position. So the GM would have to be the host, and if the GM gets disconnected, that's a disconnect for everyone. I can't see different random players dropping into the middle of a GM session being great either, they'll start out confused.
In a Pen and Paper game, wouldn't it be pretty much unheard of twenty sessions in for Bob to leave, and then Clive joins the group and then starts playing Bob's character?
Perhaps I'm not using the best word for this saying Drop in and Drop out, that is a MP style unto itself. But playing MP DM games with strangers. But again that may not be what D:OS2 is about, D:OS surely wasn't. But if we can create our own content perhaps that content is targeted towards more random players coming together.
But if there is Drop In/Out, yes that seems like it would exclude the GM, I would be thinking randoms jumping in and out as PC's only.