I’d actually forgotten about this issue until I recently came across mention on the TfL site explaining that you can link authorised user cards to an online account. Originally there was a problem where the name on the card did not match the name that the bank statements were sent to. I had tried to explain the problem to both TfL and my bank, but neither seemed to understand what was wrong.
However, I can now report that my wife has successfully added her payment card to her own account, even though the card is linked to my card account. Now I need to dig out my paytag and find out if they’ve fixed the issues with that too. Watch this space.