Handle over the line item after adding to cart

I develop a new module for customizable product options. Therefore I add some new fields to the add to cart form. The problem is now I need to know which line item is added, because I need to link them in the database. (The project can be found here: Commerce Option.)

To track the line item we should reassign it to the $form_state after we changed it. Here is the patch for this. I hope these changes are welcome and someone can add them to the core.