Frederik J. Jensen
Thoughtful Dane
Fastaval has for many years used a queue of reserves. Personnel heavy and requires games to start at the same time but otherwise works great: if you want to play but care less about what, you just queue up at a specific point at the start of the timeslot. As games start up and it is clear which are missing players, you just report “two seats free on Hot Springs Islands”. If two people in the queue want to join, you get a reply that two people are on their way.