Sounds like it's worth exploring. It could be possible, but you'll have to make the record producer or catalog item public and all variables within it. At the least, the Walk-up user record will need access. Then you'll have to figure out how to get to the form via the Walk-up portal as you won't have access to Employee Center or Service Portal unless you make a whole new portal that is all public. Can you share more on what is the use case?
