or keep it simple (if you want to expand..)
8 groups of 6: gives every team 5 games
This results in too many matches per team and overall. 5 games in first round. Finalists will play 9 games.
Gibraldo's plan keeps it at 7 games for the finalists, but he gives one extra game to the teams eliminated in the first round (FIFA gives only two games to the 16 eliminated teams). This can be a good or bad thing, depending on your view...
In Gibraldo's plan, there will be more pressure on the first game. A team which loses its first match seems less likely to advance.
Also for fairness the system relies on having accurate seeding. If pool A1 is a "group of death" (3 good teams) but A2 has (say) Germany + 2 weak teams, then Germany has a harder job to qualify in your system.
A1 : Brazil, Netherlands, Japan
A2 : Germany, Guatemala, New Zealand
Then Germany has three hard games, but Brazil + Netherlands + Japan have only one hard game.
But, this isn't necessarily a big problem. The "luck of the draw" is already a factor anyway.