It is true that the only way to charge FedEx on credit card is to charge on each package seperately. Our Amex bils is about 30 pages long every month, but I just can't pass the opportunity.
I have two approaches to minimize our adminstrative headache. First, get an additional card just for FedEX. If you charge enough, this is worth it.
Second, American Express has an online accounting function which can download your statement to a spreadsheet or an accounting software. This will make your accounting department complains less.
We still get our volume discount with FedEX through charging to our AMEX. IF we can pay by credit card, we will not pay by check.