Generate only for non-default fields

I like this for populating test data - but often I want to be in control of a couple of the structs property values, and then fake whatever's left (and not skipped). Is this possible? I guess what I'm asking for is a 'ifDefaultValueForTypeThenGenerate' kind of functionality

Also, it would be cool if there was a way for us to feed you a func name that you invoke to populate the field. Product-specific fake data that you cannot provide could be added thus.