Changing Address fields City or Postcode to Dynamic Drop Down

For ease of use, and for greater accuracy for data input, is it possible to change any of the existing form fields where address input is required such as a new contact to dynamic drop down?

I would like the user to be able to select a postcode from a drop down list and then that postcode autopopulates the city, state, country fields.

Or alternatively they can type in a city name and it populates the postcode, state and country.

I can’t seem to be able to change the field type thats already there in Studio.

Also if for some reason a postcode or a city doesn’t exist in the drop down list, they should be able to just type it in.

You would need to write custom code to handle this, it’s not possible out of the box.

Thanks,

Will.