How to remove a region from omega grid
This is actually pretty complicated.  The major problem is that both the region and the zone that it is in have the grid classes on them.

You need to implement a template_process_zone() in your theme, and then remove the grid classes from $variables["content_attributes_array"]["class"].  You then need to implement a template_process_region() and remove them from $variables["classes_array"].

Any other regions in that zone will then have grid problems, and the containing zone won't have a grid container definition.

Your other option is to use CSS to override the grid definitions for the zone and region.  Depending on your site and the theme, you may be able to get away with using a full zone wrapper around things, and then using positioning on the region to make it appear full width.