A "switchPlayerControl" event, if you know what I mean. Basically, a command like /switchplayer ______. The player whom they requested then has a prompt pop up on their screen, saying something like:
 "Would you like to switch player control with _____ (BLID____)? 
 Now, if they accept, the two players simply swap minds. Each player controls the other, what they say, do, build, stuff like that. 
I know everyone's gonna hate this idea, but I think it might just be a bit of fun.