Every Southern train I have ever caught late(ish) at night is virtually guardless while it's moving as they very rarely venture out of the compartment at the rear of the train, except to check the doors at the virtually empty stations. If you think the existing guards provide any sort of security for lone travelling females at night then - in my experience - you're living in a parallel universe
Indeed. And Southern are saying there will still be a second person on trains, other than in exceptional circumstances which the RMT agree with. In fact this second person, free of having to worry about opening and closing doors, will be able to spend more time scaring off all the rapists who frequent these services.