Football is much more popular and established game then cricket. FIFA is as big as UN, while cricket is not popular in the whole world. There are only 10 test playing countries. Rest of the countries have team just for formality. So at the moment we cant compare cricket with football. Let the cricket spread to rest of the world before we establish such model in cricket.
Popularity has nothing to do with it. Look at sports like Baseball and American football. Leagues like MLB and NFL are among the richest in the world. Let's have a 4-month window for the IPL, so that it generates the maximum revenues. The remaining 8 months can be provided to other franchise leagues, ICC tournaments and bilateral tours. At this point, the IPL is much more profitable than any of the other options. So ideally the ICC should allow it to expand. I would suggest a 20-team tournament spanning over 4 months.