I have two suggestions for the League:
1) Add relegation to the leagues. This would make it a lot more interesting. Teams who have no or very little chance of promotion can still have a reason to play. There will be fights to avoid relegation. I would suggest relegating the bottom four teams down to the lower league level. This would also result in inactive users eventually falling down to lvl 1. This would also keep more and more people from continually filling up the max league level, because some would get relegated.
2) Make it harder to get promoted to the next league level. Right now, it's too easy to get to the next level. With the top seven teams making it into the next league level, you don't have to be very good to get promoted. As long as you aren't bad, you can make it into the next league level. If only the top 4 teams made it into the next league level, it would make top eleven more challenging. It would make it more exciting when you do level up, because it's actually an accomplishment.
This system would also have the same number of people relegated and promoted, so there would always be the same number of people in each league. It would make Top Eleven much more interesting and fun.