Date form field type

First of all, thank you for such well-written library.
I need to have ability to enter dates with:
* customizable UIDatePicker replacing the keyboard
* (optional) custom NSDateFormatter

AFAIK there's no way to do this. I'm going to create EZFormDateField class. Please advise how it should be best integrated into existing class hierarchy.
I supposed to subclass from EZFormTextField, but this class assumes that actual field value is NSString (not NSDate).

So, is it good idea to subclass from EZFormGenericField?

Thank you!