We would love to see the lookup ID field located in the registrant form. Upon first glance, this would help to confirm we have the correct registrant.
In addition, when looking at the registrants that come in from online batches, we can immediately see if we are looking at a new constituent to the system. Before committing the batch, it is possible to search to find those with similar names to decide if the constituent should be added or if the person is a duplicate and should be replaced with the constituent already in the database. Without the lookup id, column it is harder to know if the search has been done and whether or not the constituents in the batch are new to the database or not.