How do you add a form to a content type?
If you are ok with custom code.


The form does not need to be inline to Content Type.
Consider this example
You have custom form. form builder of which takes an argument as nid.

function custom_form_builder($form, &amp;$form_state, $nid) {
   $form['nid'] = array(
     '#type' => 'hidden',
     '#value' => $nid, 
   );
  // form field goes here.
}
Now in your view add nid field along with other fields you need and an extra custom field.
In your views you can define custom template for custom field.
Implement template_preprocess_views_view() to call drupal_get_form('form_id',$nid) and make it available on the custom template.
Print the form on the template.
Now when the custom form gets submit you can get the nid to update in $form_state['values']['nid'].