Agree with the facing of stronger teams but that is just part of the game. Sometimes you win, sometimes you loose. It is a free gift after all. Even it would have been a 2 week challenge where you will face every advisary of the league, you could complain about having home matches against the strong teams and weak advisaries in the away matches for instance. For every challenge some will have luck some will have none.
It is also something that is under development and right now I have to say it looks nice. I do think that more insight in the game is way more important than challenges. A lot of football manager players as statistics freaks. They want to understand the game and use their mathematic skills to beat the system. But right now there is no insight whatsoever. It is not possible to calculate anything. It is not possible to tell what the effect of SA are. It is not possible what the effect of training is, etc..... which is pretty ridiculous for a game like this.
But alas we are not getting answers to that apparantly. So back to the subject, challenges:
1. The no SA challenge: Goals scored by players without SA
2. The attacking challenge: Most goals scored using hard attacking only in team mentality
3. The defensive challenge: Least goals conceded using hard defensive only in team mentality