Custom map fields

In MailPoet 2 and in the new beta version, the subscribers only have two separate fields for first and last name. In Dutch a lot of people have a – as we say – tussenvoegsel (or in English a surname prefix). It would be nice to have a separate field for that. Is it possible to create it e.g. with the function.php functionality or is it maybe something for a feature request?
I’m using Gravity Forms to automatically map subscribers to my lists in MailPoet, but I’m missing the surname prefix in a couple of names. 🙂