Another option may be to analyze the businesses pursuant to FIN-2012-G001 and determine if they are not operating independently.
But this still does not alleviate the need to properly identify the conductors of the transactions.
I did not suggest that it relieves you of that responsibility. My point is that it may be logistically easier for the original poster to group the relationship in that manner if it can be deemed appropriate.
That way, they can
aggregate the cash under all circumstances, even if they were unable to identify a conductor on a transaction which would mean the difference between reporting all of the cash and not reporting any of the cash.
I agree with you that it's a best practice to implement systems that will identify every cash depositor, but as I'm sure you're well aware, there are plenty of core systems that don't have same day aggregation and plenty of banks that made a justifiable risk-based decision to set conductor ID thresholds.