Not only an international calendar, but an alternative to FIFA rankings, and as part of an international calendar:
At the start of each year, the teams are broken down into groups of 32 based on the previous year’s rankings – the first 32 in Group A, the second 32 in Group B and so on.
The teams in each Group play matches over the course of the year based on the Swiss system. For a Group of 32, a minimum of 5 games per team would be required. It might make sense to play an extra round to make 6 games per team, an even number.
The teams are ranked according to the Swiss system. That’s the ranking for the year. The team at the top could rightly be called World Champions for that year.
You could have promotion and relegation between groups.
Effectively, you have a World Championship every year.
Each team would play as many games at home as away, in the same way that “In chess it is also attempted to ensure that each player plays an equal number of games with white and black, alternate colors in each round being the most preferable, and a concerted effort is made not to assign the same color three times in a row”.
The rankings could be used to determine qualification for each confederation’s continental championship, which could be held every two years (years ending in odd numbers).
The teams that get through to the later stages of the continental championships qualify for the following year’s World Cup, also held every two years (years ending in even numbers).
Do away with the current methods of qualification for each continent’s championship and the World Cup.