If you go to "My Games & Apps" navigate down to "Full Library" and then go to the "Game Pass" tab, click "Filter" and then "Surprise Me" it will randomly select a Game Pass title.
Maybe you could do something like that? Have someone in charge of picking a random Game Pass title every month and whatever they get from the "Surprise Me" button is what others taking part have to play?
Oooor maybe use the Surprise Me button a few times and then vote on the titles it randomly selected?
For example, I just did it 5 times.
- Blinx The Time Sweeper.
- Chained Echoes.
- Zoo Tycoon.
- Hitman III.
- Crossfire X.