How about some diversity issues?!
In RL there are teams which buy perhaps an asian or turkey star to earn more money on merchandising. So perhaps you could include a diversity-factor in these incomes(Sponsors and Crowd). The more diverse a team is, the more it could earn. In Hattrick i'm forced to buy native stars because of 20% Bonus on foreigners. I think it would be better to pay a one-time fee for perhaps a language course. Just an idea...
Cheers
Tattoro