Say a guy 6' 200 lbs has 75 speed, 75 acceleration, and 75 ball carry theoretically you could time his 40 yard dash on a break away during a game. Pending a bunch complicated of equations combined with trial and error a sort of combine result would be possible for me.
Limited it may be I would love that for the draft. Still, a real nfl player is rarely running untouched for forty yards. For me it is personal. As I would use combine numbers to add some relation to real life, but they do not change actual gameplay.
In real life, for me, combine numbers are some sort of bar of measurement, but by no means of a tell tale sign of NFL talent. It is finding that fine line of physical talent vs. technique.