Changes suggested

If possible, don't overwrite all submit handlers when altering a form
instead of

$form['#submit'] = array('_modules_batch_submit');
do
$form['#submit'][] = '_modules_batch_submit';
if you have to remove existing submit handlers, use array_search() to find the index and remove it with unset().
Otherwise you might overwrite the changes of other modules.

$context['message'] = t('Uninstalling %module Module', array('%module' => $module));
When you print that message out you actually already have uninstalled the module. So the sentence should be in simple past.

As already mentioned, try no to use drupal_goto() whenever possible
$context['message'] = t('Disabling %module Module', array('%module' => $module));
Should be "Disabled %module"
$context['message'] = t('Enabling %module Module', array('%module' => $module));
Should be "Enabled %module"

by patrickd