I have 2 modules. Let's call them Publisher and Publication for discussion's sake.
Publication module requires Publisher module. Publisher module provides form to edit publisher's data. Publication module provides list of publications with reordering and adding capability, and it can be limited to display only publications by one publisher.
Now, I want to nest publisher's publications form at the bottom of his data edit form. I would prefer to avoid writing same code again - I want to keep validation functions and submit functions as they are now, just have it on one screen, with one submit button.