Are you defining lead angle as the bearing to target expressed in number of degrees from the bow, as in the German bearing system?
If so, you're onto something with some playing around. All by itself, it means nothing. BUT if you put yourself on a collision course with the target, that is the bearing to target doesn't change over time, THEN his speed is a known proportion of yours based on the Angle on the Bow. (unless his AoB is zero or 180, in which case the target speed is undefined)
I don't have my drawing software right here at work, but I could work it up and shoot you the diagram for you to troubleshoot the rest of the way if you'd like. You're onto something really useful here.
