Hi, 

You can use a combo of getting player ID through Peer ID and invoking a log event request onbehalf of the player that removes them from the session.

Something like this:

in RTScript:

var matchID = RTSession.getSessionId(); //Gets Match Instance ID

var playerID = RTSession.getPlayer(peerId).getPlayerId(); //get player ID

var request = RTSession.newRequest().createLogEventRequest().setEventKey("Event_Name_You_Specify");

request.setmatchID(matchID);     // Make sure log event has string attribute with same shortcode

request.setPlayerId(playerID).send(function(response){             RTSession.getLogger().debug(response);         });

Log event cloud code:

var matchID = Spark.getData().matchID;

Spark.getMultiplayer().loadMatch(matchID).removePlayers(Spark.getPlayer());

With this combo you should achieve it.

Cheers,

Omar