We create customized and personalized products. After selecting the items they want, the customer will send us the wording/logos/etc that needs to be placed on their items. Oftentimes, a customer may make changes to the order after it's been placed, and that may change the total they're charged. We need a way to capture the credit card info and charge it later - or not capture it at all and generate an invoice.
Setting a specified auth amount might get around this, but as mentioned in your wiki it can pose problems if we're holding onto the amount for an extended period - and if our customer takes longer to make up their mind (which happens more often than not), the auth might expire.
We're also looking at integrating FoxyCart into our Quickbooks accounting system, so could it be possible for the customer to select a "pay later" or "Quote Only" option during checkout, that would then generate an estimate?