Right now, the koha selfcheck will only allow use of either cardnumber or username+password. We should extend those options. First, it'd be good to make the password requirement a separate question, thereby allowing cardnumber+password and username alone. Second, we should allow the possibility that a unique patron attribute might be used at checkout on a selfcheck (with or without a password).
I especially agree with Andrew Fuerste-Henry that a unique patron attribute might be used at checkout on a selfcheck. We will soon find ourselves in that situation. My university will enable students to use up to three smart devices (phones and watches) instead of their barcoded ID cards. Each smart device will have its own unique ID number. It will be important that students be able to use those devices at our self-check stations.
I know Swedish libraries are often used to having multiple cardnumbers/IDs per patron from their old systems, and are somewhat disappointed when this is not possible in Koha (although we have usually found a way to work around it, so far). If we do allow for this, we must make sure it works for all sorts of loggings in, like SIP2 and ILS-DI too.
This hasn't been very active so I am adding my .02 worth. I think this would be a great added feature. We have patrons that have been asking for this as a option.
My main goal at the library is to provide excellent customer service. While we have moved to digital cards that are more accessible via mobile phones, adding another checkout method would further promote customer satisfaction. Especially since patrons constantly ask about this feature.