I'd start with an understanding of what your policy (if any) says about closing accounts for recurring SAR filings. If you do have such a policy, you need to follow it. In the absence of policy, I'd recommend you determine what it costs to continue whatever extra monitoring/due diligence you do in order to keep the customer on your radar, analyze activity and file those quarterly SARs. Share that cost estimate with the appropriate people and let management make the decision on whether to close out the account. You already know to expect push back from your lending management.
If structuring is the only suspicious activity you see, and there's no apparent safety and soundness risk in maintaining the account relationship, I don't think you'll be challenged by examiners for keeping the account open if you've done your homework and documented it.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8