allowed dojo banning, made dojo mobs dust upon leaving

code/datums/elements/dusts_on_leaving_area.dm

@@ -0,0 +1,28 @@
+/datum/element/dusts_on_leaving_area
+	element_flags = ELEMENT_DETACH | ELEMENT_BESPOKE
+	id_arg_index = 1
+	var/list/attached_mobs = list()
+	var/list/area_types = list()
+
+/datum/element/dusts_on_leaving_area/Attach(datum/target,types)
+	. = ..()
+	if(!ismob(target))
+		return ELEMENT_INCOMPATIBLE
+	attached_mobs += target
+	area_types = types
+	START_PROCESSING(SSprocessing,src)
+
+/datum/element/dusts_on_leaving_area/Detach(mob/M)
+	. = ..()
+	if(M in attached_mobs)
+		attached_mobs -= M
+	if(!attached_mobs.len)
+		STOP_PROCESSING(SSprocessing,src)
+
+/datum/element/dusts_on_leaving_area/process()
+	for(var/m in attached_mobs)
+		var/mob/M = m
+		var/area/A = get_area(M)
+		if(!(A.type in area_types))
+			M.dust(force = TRUE)
+			Detach(M)