How are you proposing to detect country? no automatic, add an additional entry to the tor directory. For a human there is no problem to get the country out of traceroute. For new tornodes it can be asked direct within the registration process.
how about "built-in geoip code". Vidalia and TorK are currently using geoip services from external sources. Rather than implementing this feature server-side and routing requests through the tor network, every client/node can _have_the_option_ of downloading an updated geoip database from a trusted source and using this would-be client-side implemented feature without recourse to external sources to: A) detect "the other" node's country (to filter Exit Nodes perhaps using a ExitNodesCountryCode and StrictExitNodesCountryCode options in torrc). B) adding a "CountryCode" descriptor to their own directory descriptors to be identified by clients with no geoip database. --Yousif