I think you would benefit from really looking into the anatomy of the ACL, and the idea that it is structured with mlti-directional fibres. It's role is not purely to prevent anterior translation. It is also one of the main involvers in the final 'screw home' movement in knee hyper extension.
It is also important to look at the stability of the other ligaments too, especially the MCL as if there is laxity here then it may be that the ACL is brought into play to prevent genu valgus deformity