Our manager would like to start preparing and filing UCCs as part of the document preparation process. This would mean that the UCC would be filed in advance of the security instrument being executed.

Is this legal?

Any opinions on adopting such a process?

UCC 9-509 says the lender can file if the borrower has signed the security agreement, or if the borrower has otherwise authorized the filing in a signed or otherwise authenticated record. That means if you want to file in advance, they need to consent in a signed/authenticated document before you file. It can be in a loan application or a standalone consent or a letter.