I have tried looking at what kind of national GD threads that has been made before, and apart from a couple of old South Africa threads, a China, a Russia and a Brazil etc. there has been a number of threads made for country's that no longer have a national GD:
Zimbabwe June 2008-July 2008
Wales March 2008-February 2009
Scotland September 2009
Pakistan December 2009-August 2010
Gully Foyle's African News Thread January 2010-November 2010 #
Poland July 2010 (2 days!)
Middle East December 2010 #
Egypt August 2012-September 2012
Greece December 2012
Austria June-July 2013
Israel June-July 2013 #
Sri Lanka (1 post!) July 2013
# for ones we have talked about
So a lot of quick deaths, so they need to have link and be about a major country or one with a large interest.
Maybe we could start megathreads in particular issues that pop up again and again (like, say, gay marriage to avoid new threads every time something happens).
That might be a good idea, but it should only be a few topics and its even more important with links for them, since they tend to die quicker.
Afleitch made one about Devolution, that never caught on. I suppose EU and UN might be possibilities. Generally I am a little sceptical of this, though. I think they are harder to maintain than big country GDs. But it would be worth trying a handfull to see how it goes, if they are linked to.