I mostly agree with your suggestion, i picked to consider the lowest skilled player, but any of those suggestions might have some sense.
However, there's another important factor that determinates how useful is the offside trap IRL, and it's not considered currently: defensive line.
In current GKO match engine, you can play contain strategy, very deep defensive line and it will have the same effectiveness than playing all out attack strategy, defensive line forward, no matther wich combination you pick (even all out attack/very deep), any combination works exactly the same and that is completely wrong.
In real life, if the distance between your keeper and the defenders is lower than 10mts, offside trap is impossible to execute, and if you play a high attacking style and your defenders are close the midfield in attacking situations (defensive line forward), execute an offside trap succesfully is really difficult (because any plyer behind the midfield doesn't need a defender to be onside). In other words, it's all about player's distribution in the field and also each playing situation.
So, i think that:
* The general offside trap formula should consider any of Brian's suggested changes.
* Offside trap should be disabled when playing very deep defensive line.
* Using offside trap and defensive line forward should have an extra penalty on its success rate, also the chance to avoid offside trap should be higher when playing counter-attack.
What do you guys think about it?