Can I create an external learner without a user ID?

We have a situation where a client wants to create external learners for the sole purpose of tracking course/class attendance, but these individuals will never sign into ELM. When creating an external learner, you have to assign a PeopleSoft User ID. And the way this field works, it has to be a User ID that hasn't been assigned to another learner. We can always set up a shell user ID for each external learner we want to create (which is probably what we will need to do), but that seems an unnecessary extra step. Perhaps we could modify that page