This is a good suggestion - I believe prefix match should weigh more than partial infix match.
As for "too complicated" - I am not suggesting to extract GDP or population data in Javascript. But in static HTML on server side you may add additional "weight" attribute to each option, the way alternative spellings are added (look at the HTML source). And then you may manage these weights externally.
I believe prefix match should weigh more than infix match... except for countries that start with an article (The Philippines, The Netherlands) where infix match works better. The Netherlands is now number 11 on the list after typing "Ne".
As for "too complicated" - I am not suggesting to extract GDP or population data in Javascript. But in static HTML on server side you may add additional "weight" attribute to each option, the way alternative spellings are added (look at the HTML source). And then you may manage these weights externally.