Sorry for joining in late... Go for it sandy.. Its a fantastic idea.. Would surely be a crowd puller as well.
I agree with sandy. It would be enough to have a pool of players and we can shuffle them around acting like a manager of the team.
I already have half my team ready
I would suggest we should implement transfers on transfer window basis. This will make sure the person best managing the available resources wins.
Also the above points system suggested by sandy seems to be too unfair for defenders and midfielders(esp. defender, now we all know it takes once in a blue moon for Rio ferdinend to score a goal

)
I suggest the points for clean sheet should also be passed on to the defenders. Also if a defender scores a goal this this should yield him more points.
Something like what i have mentioned below:
Goal scored by defender/goalie: 5
Goal scored by midfielder: 4
Goal scored by a striker : 3
Clean sheet:
Goalie:5
Defender:4
midfielder:1
Captain doubles the points..
Yellow card/red card rules as suggested by sandy
Penalty shootouts should be out of the points equation..