That may be the issue, I know that the B315 that Vividwireless works, but if its outside of that then that may have had a different IMEI range then Optus has allowed.
IMEI is the unique identifier that provides detail to what hardware it is, Optus use this in the filtering for these devices.
Nowhere does it say the devices must be purchased directly through Optus or Vividwireless's retailers.
As for them adding it - not sure on that side, seems an uphill battle.
Would it be locked by IMEI or by MAC address? Doing by IMEI would require some sort of device registration process when you BYO approved device. MAC would allow certain manufacturers (and maybe models, not sure) to be identified.
What happens if you change the MAC access on a non-approved device to that of an approved device? Would it work then?