That’s a neat use case! Ideally it would be possible to create assets directly from Field Kit… I think there would be other similar use cases for creating assets on the fly. Hopefully one day!
Re: a cronjob-like way, one thing we have discussed in the past is the Drupal Rules module. It would be neat if we could define rules for all sorts of different things. Check out the comments on this post: Schedule a log based on a quantity value