I've always like the idea of a proper 2 tier "X Nations" - Tier 1 and Tier 2 with promotion and relegation, or at least a play-off. That would certainly allow Tier 2 national sides to have something to aim at, with a chance to expand and improve the game in their region. When Italy joined the 5 nations there was a lot of scoffing and the assumption that they would be perennial wooden spoon candidates, but they have taken some big scalps and improved hugely over the years.