[Hi from Argentina, where our national sport is opining about soccer and our second national sport is soccer.]
I remember that someone posted a worldcup simulator during the championship. https://news.ycombinator.com/item?id=7941898
After playing a little with it, my takeaway was that the FIFA index is worthless (too political?) so I'd remove it from your model. Also, the ESPN index was one of the better predictors, so consider adding it to the mix.
