I haven't thought this all the way through but I know how you can have events randomly select things.
Let's say you want events to randomly select one option out of 8 different options. Somewhere in the build, hidden in a place where no one will find it, place a 1x8 brick, and parallel to it place 8 1x1 bricks. Have the 1x8 brick fire an ordinary gun bullet in the direction of the 1x1s. The bullet will fire from the 1x8 in a random location along the brick, so it will hit a random 1x1. Then you can put different events on each of the 1x1s.
As for having it randomly select players, I'm not sure. One thing you can try is have each player on a different spawn point, and have the 1x1 randomly selected by the bullet send a relay to one of the spawn points that activates events that teleport that player somewhere and changes their datablock, but that's not really an effect method because it might randomly select a spawn point that there isn't a player for. Maybe you can use the pong projectile to check if each spawn point actually has a player on it before randomly selecting one, but I don't know if that would work.
I hope I was helpful somehow.
