Here is an experemental rule for Harlequins:

Cegorach, The "Laughing god" has decided to inconspicuously join a troupe to assist them in shifting the battle in favor of his master plan. Designate a random model as "Cegorach", as he travels in disguise. The troupe benefits from his presence in the following manner: The Harlequin troupe gets a 4+ invulnerable save, as long as the model remains on the field of battle. The cost of this is +100 points. The "Chegoach" model fights as normal for whichever Harlequin type that is designated. The "Chegorach" model can not be killed. If the model in question is "Killed" It is insted removed as a casualty and has "Vanished" from the field of battle Nanoseconds before the "Fatal" attack, With an echo of laughter, (having tricked an enemy, and saved a harlequin from that fatal blow).