I don't know that it can be done. Currently it appears there is only one line available for the iPhone to use for Caller ID. There is a second smaller line that is used if you have the person in your contact list that shows which phone number it is, i.e. mobile, home, work, etc.
The only issue that I would see with that is for businesses that have PBX systems and the phone numbers they call out from don't always match what number you have entered in your phonebook. Also, when you get a call from a number you don't have entered, all you get is the number line from Caller ID, not the name of the caller and/or business, even though this information is sent through Caller ID. I guess it is an enhancement we could ask Apple for on their feedback page.😕