First, you don't need to type any area codes if they're saved as a contact in your phone with the area code. I assume you realize that.
Therefore, the only numbers you will have to type in the area code for are ones that you don't call often enough to have in your phone. So if you don't call them often enough to save in your phone, is it really that much of a hassle to just type the 3 extra digits? Or just save it in your phone.
Just so you know, I'm not trying to give you a hard time. I am in the exact same situation. I live in a different area code from where my phone number was issued. If I'm calling for a pizza or some other business I have gotten in the habit of just typing the area code. If it's a friend (even someone I've just met that I may never call), I will just add them to my contacts. Granted, this means I have over 250 contacts, but if you go through them every three months or so, you can get rid of the old ones quickly.
Sorry this doesn't exactly answer you're question, but maybe it can be a solution that will work for you.