We went from our own online ticketing system to a Lufthansa owned system called myIDtravel. Works quite well, both standby and non-standby tickets are available based on Z fares, chance of acceptance is shown during booking/listing. One downside is however that payment is via credit card only and is deducted at booking, if you do not fly the booked sector you can get it refunded, however a fee of 1,50€ is deducted for the service.