What if FIFA uses the serie of 5 format?

After the Baseball World Series, we're also now in the middle of the MLS playoffs. I got to watch San Jose beat New York 1-3 and qualify for the final of its conference against Colorado. 

The format the MLS has chosen for its playoffs is a similar format than most football competitions. It's basically 2 games, one at home and one away, with the team scoring the most goals qualifying. In case of a tie, they go in extra time and then penalty kicks. 

I'm used to this format, and quite like it to be honest. I think it provides enough time so the best team should win, but at the same time, offers opportunities to the underdog to make something happen. 

Now, I was debating whether football shouldn't use a longer serie format for a final. For ex, best of 5 or even best of 7. In other words, the first team who win 3 or 4 games is declared the winner. 

At first, I'm sure all the folks who've been watching football for a long time will say this is totally absurd. I'd tend to agree with them. After all, the beauty of football is that the underdog can always win and such series tend to favor the best team. So in spirit, it's easy to just ditch the idea. 

Now, let's look at the previous FIFA World Cup. What if the quarter-final and semi-final would be played with a serie of 5, and the final with a serie of 7? 

1. We would get a much longer competition with more of the top games. Who would complain if we get to see Brazil & Spain 5 times more? It's harder to organize, but would generate a better show for fans, and more revenues for the federations and the host country. 
2. You're guaranteed to see the 2 best teams of the world in the final. With direct elimination, while the emotions can fly high, a team who doesn't play well can go through (one could argue that this is what happened with Netherlands).  It's not the case with a serie of 5. 

So it's not totally silly. Not saying that it must be done, nor that I won't miss the emotions that direct elimination can create, but I'd be curious to see what this could do if implemented.