Huhu,
the partys doesnt work correctly - at first the trapper doenst accept the defendflag - he will stay still when you active the citydefendmode - also your villager has only a 1 square sight so they will stay still also when next to them other villagers fight - when they move more then this 1 square they will cancel the attack and run back to the flag - so the flagsystem is at the moment only a gimmick which can kill your villagers xD