I have a simple requirement, sync the

shipcomplete

field from the transaction form to a checkbox in checkout. Is there a way to pass a native UI field through to the front end? Any suggestions?

You might to create a module to be added on the checkout and make a small service to fetch the field to display it on the front-end. If you field is just for displaying purposes, you could create a custom field that is sourced from the shipcomplete and the expose it on the configuration record, then just display it on the front-end (I'm not completely sure that would work for you)