Entering Base Overrides for individual customers on same worksheet

Client wants the ability to enter base overrides for specific customers.  This is not a big issue.  Using standard functionality, we can just create a worksheet filtered for a specific customer (e.g. customer A) and then enter the base override.  Then the entered override value is applied (and proportioned, if necessary) to customer A combinations only.  Similarly, we can do the same for customer B:  create a worksheet filtered for customer B only, enter overrides and values are applied/proportioned to the Customer B combinations only.

However, client is saying that maintaining the customer-specific base overrides on separate worksheets is un-manageable and they want to be able to view the baseoverrides for each 'customer bucket' on the