My preferred implementation-- it couldn't be that hard to create a new workflow rule option, so that I could check new applicants for jobs against an already-submitted list and take appropriate action. 

e.g. if the applicant's name is on the list for a given company, then trigger the rule. Maybe we have a larger text area and can use the "Found" operand or something. Usually the dupe lists go with a specific client/company. There are several potential implementations that might work. 

In general, i'd really like to see the capabilities of the product expanded thru enhanced workflow automation capabilities. For example, I'd really like to pre-screen inbound applicants fields against job fields, and automatically toss out candidates that don't meet the criteria. e.g. If the job says no H1's for the work authorization then I want to setup a workflow rule to send them a courtesy e-mail that says we can't move forward and why, and have it automatically send the mail and revert the candidate's status, etc..  These are the types of minor product changes that have large impact, and save hundreds of hours of time. 

A lower-priority feature idea would be to create a soft toolbar warning in the submission UI to warn of a possible duplicate submission. Kind of like the new Outlook Send restriction features in Exchange 2016. However, in general that is too late in the process to be effective, as by that point my folks would have already wasted time with the candidate. 

John