Is it possible to determine the point (on the other object) when a kinematic/trigger rigidbody hits another object?
Maybe this one:
http://unity3d.com/support/documentation/ScriptReference/Collider.ClosestPointOnBounds.html
It is not going to fix entirely your issue but that might be the closest to.
Also, it returns a Vector3 so you could use that for what you need.