sorry, too less reputation to add a comment...
Nice suggestion but the Show Field doesn't contain all properties from
the user profile service. I can't see any settings within the user
profile property settings page to get extra options to appear.
if you want to show custom properties in "Show Field" section of an SPUser field, you have to configure this fieldproperty in the User Profile Store as "Indexed".
Indexed properties are crawled by the search engine and become part of
the People search scope schema. Only index a property if it will
contain relevant information for people finding or if you want the
data displayed in people search results.
UPS in CA >> Manage User Property >> Edit "Country" field >> Set "Indexed" to true and Save..
After that you have to start the "User Profile Service Proxy - User Profile to SharePoint Full Synchronization" Timerjob...