IMHO, I may be getting confused with what you're trying to say - the application as a piece of paper, or a request for credit.
As a piece of paper, it should be immaterial (except for the date) if the information is the same, and the bank is trying not to inconvenience the customer. It might be best if a copy of the original were used, and the customer(s) initial the intent to apply jointly, update the employment and liabilities section and re-date the application. If it were electronic, it would be easier.
As a request for credit, there should be no confusion between old and new applications. What happened 6 months ago is history. This is a new request, along with all accompanying timeframes and disclosures.
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Integrity. With it, nothing else matters. Without it, nothing else matters.