I'd love a different football game on mobile. I really got into PES 2008 on mobile, which at first I thought was too fiddly on an N95 but proved to be quite decent in the end.
My two cents: Football is far too detailed and varied to be recreated really well in a simulation style on a mobile game. PES 2008, Real Football and FIFA on mobile have probably got this market sown up anyway. I'd really like to see something different, like Proxi suggests.
I've been thinking recently that a turn-based footy game might be good. Not a drab, Subbuteo-style game, but imagine a football game in the style of Advance Wars (bear with me). Each player would take it in turns to move all of their players around the pitch. While in possession, the idea would be to work your way up the pitch while moving your other offensive players in positions where they can receive the ball. When in defence, the aim would be to anticipate these moves, steal the ball and mount a counter attack.
The pitch would be divided into movement squares, such as in AW. Obviously different types of players would have different attributes, eg. wingers would have greater range of movement in a single turn than centre backs. The 'battles' would take the form of one-on-ones, where if you got into the adjacent square to the possession player you can make a play for the ball by 'attacking' them. Just as in AW, where different units have strengths and weaknesses against each other, different players would have different tackle strengths. So for example, a tough centre back can dispossess a sprightly forward in a single turn, whereas it would take two or three turns for the small striker to dispossess the centre back.
Other attributes would be passing range/accuracy and shooting range/accuracy, which of course would vary depending on the player. Each time a player opted to pass, an accuracy rating would appear next to the target. For example, a Pirlo type player would be able to ping a cross field pass with roughly 75% accuracy, while a clod hopper would have a much lower rating for accuracy and would only really be useful, passing-wise, for short range moves.
There could also be special abilities, ala Advance Wars, which are charged up as the game progresses which could be player or team dependent. These could include super slide tackle, where any player is dispossessed in one turn, sniper shot, where shooting range is temporarily increased, super dribble, where the player is immune from tackles for one turn etc etc etc.
I think graphically it should be over-the-top cartoony style, in keeping with the gameplay, rather than balls to the walls realism.
Obviously needs work, but I think it could be good.