Looking for code review for custom field_group formatter "form"

I've built a new field_group display formatter called "form" to display the contained fields in a form, allowing users with permission to update an entity the ability to do so right form the "view" of an entity.

This is similar to editablefields, except that in this case I want to be able to display multiple items with 1 submit button, and would also like to have different view_modes for different roles, thereby allowing different users access to different parts of the entity.

The attached code does its job well! However, there are a couple quirks that I would like to get some guidance on if any one can assist. Specifically:

1) The only way I am able to get the form to actually display within the field_group element is by rendering it and forcing it into the $element's markup:

<?php
$element['#markup'] = drupal_render(drupal_get_form('field_group_form_build_form', $group, $form));
?>

This feels a bit brutal, but it's the only way I've been able to get this to work and for the $form_state to actually exist properly throughout the form validation and submission process.

2) Because this is all done at the pre_render (theme) layer, any form error messages set during validation aren't visible until the next page load. I have overcome this by doing the following on the _validate() level:

<?php
$form['field_group_form_fieldset']['errors'] = array(
  '#markup' => theme('status_messages'),
  '#weight' => 0,
);
?>

but again, it seems a bit brutal. I would hate to display any other messages that I don't care about within this field_group. Ideally, I'd like the messages to display in the standard $messages variable at the 'page' level.

Outside of these 2 it's working well, and there's not too much code here to achieve this functionality so I'm fairly happy with where it's at. Module is attached.