OSProperty - Hard Coded Select Option for Regions

We'd like to restrict the available options when users are adding/editing the Region field in Joomla's OSProperty (see attached images for reference). We're thinking the easiest route would be to hard-code the options available, implemented in the layout folder's '[login to view URL]' file. Essentially we'd need maybe two or three options added to the select box to get started and then we can add the additional ones from there. The select box would not be dependent on any other field.