Just as supporters can opt to have their teams results kept secret to allow them to see a replay, i think it would be good to have the same option to watch your national teams games.
im not sure how much demand there would be for this, but certainly i could never watch an U21 game because they start during working hours, but maybe this isnt a problem for all nationalities, and those with no jobs!
it may also be an "easy" thing to add to preferences, as there is already the facility there to do it for your own team?
i dont know im not a programmer :/
Anyway i hope this will be considered one day :)