As this is a user-to-user forum, you likely won't get any authoritative response from forum members. We generally help each other figure things out where possible, but we're (almost all of us) just members like yourself, and all the time we wonder ourselves why different changes are happening. But perhaps somebody here does have info, we'll see if anyone respondsWhy was b/pay removed from the system that worked really well for people?
I'd think that you might try using the local leadership chain there in Australia. It sounds like there might be a number of members there who previously used this system (including Bishops, Stake Presidents and Area Authorities who also pay tithing), and if there's feedback from all of you through your leaders, that might have a better chance of (a) determining why this change happened, and (b) seeing if either there's an alternative or if there's a possibility of getting it returned.