First of all, this is a great post and one that I have found very useful so thanks for the hard work. I have a question about balance.
I do not know the mechanics of the game but it seems to me that your description of balance is perhaps a little understated. I think its one of the most important attributes within the game. We've all heard commentry IRL about players scuffing shots, or mis-placing passes becuase they are off balance, however your discription seems limited to shoulder to shoulder confrontations.
I was always under the impression that balance provided a small modifier to most actions performed by the player. for example, the ME asks the player a Yes/No question regarding balance, when he performs an action. If the player is not balanced then it creates a negative effect on the action and he wont perform that action to the best of his capabilities. This would effect many in-game actions (mainlly technical execution), including passing, tackling, shooting, running, dribbling, set peices, heading. skiddy wet surfaces would also have an effect. IMO it makes balance almost as important as decisions and anticipation, due to the number of activities it can effect. It also brings up the question, is balance measured by yes (off balance) or no (perfectly balanced), or is there a scale involved to indicate how off balance they are, the worse the balance the bigger the penalty?
Also regarding the shoulder to shoulder action. I think your putting too much weight into the attribute. When a shoulder to shoulder competition is in effect, the stronger player will win regardless of balance. The result of the victory will cause the loser to become unbalanced (and more), however if his balance rating is high he can recover it quickly (in case of a yes, no balance scale) or will only be given a minor balance penalty(in case of a larger scale), before performing his next action.
Like I said though I dont know much about the match engine, and I am speculating about this via my own in-game experiences. Does anyone have any comments on this?