There's no simple configuration option for that, no...that's a pretty big change to how that payment method works. More importantly, there'd be a lot of work in models, controllers, gateway logic, etc to get the store to save the PO information when it thinks the customer is paying by CC.
It seems like it'd be easier to add a new field to the existing views where you want it, and then add a little custom logic to get it saved where you want.