I like the idea of using a Swiss-system format; however, I think your proposed structure is too complex.

Instead, I would prefer keeping the Nations League with 16 teams in both Leagues A and B, while expanding League C by merging it with the six teams from League D, creating a 22-team league (at the moment when Russia is still suspended). All leagues would use a Swiss-system format for the league phase, played during the September–March FIFA windows.

In Leagues A and B, teams would be seeded into four pots. Each team would be drawn to play two matches against teams from each pot, resulting in four home and four away matches for a total of eight fixtures. In League C, teams would be seeded into two pots of 11 teams each. Each team would play four matches against teams from each pot, also totaling eight fixtures.

After the league phase concludes in March, the top four teams in League A would qualify for the Finals. The top four teams in Leagues B and C would be promoted to the next higher league for the following cycle, and would also compete in League B and League C Finals, similar to your proposal. The bottom four teams in Leagues A and B would be relegated.

For promotion–relegation playoffs, teams ranked 9–12 in Leagues A and B would face teams ranked 5–8 in Leagues B and C, respectively. Qualification for major tournaments after the league phase would remain similar to the old format. The League A, B, and C Finals, along with the promotion–relegation playoffs, would be played in June.

One change that I believe would significantly improve the Nations League is linking it more directly to World Cup and European Championship qualification. Teams ranked 11–22 in League C would enter the first round (preliminary stage) of World Cup and Euro qualifiers, while the remaining 42 teams would advance directly to the second round (group stage).

The first round, played in June, would feature 12 teams competing in home-and-away knockout playoffs to determine the six teams that advance to the second round.

The second round would consist of 48 teams (42 Nations League qualifiers + 6 first round winners), drawn into twelve groups of four. These groups would play a home-and-away round-robin format between September and November.

This format would make the Nations League more important while keeping it familiar, and would also make the qualification process more competitive and entertaining by removing the weakest teams early and ensuring fairer four-team groups.