Roothog,
I get what you are saying but say the difference between a fast stride vs a slow stride is what in MPH? 1 or 2 at max. So if I take a guy with a whip who snaps it at 100 vs 98 does this make a lot of difference? I don't see it. Certainly part of the teaching on throwing hard is about tempo.
Again I am not sure, but having been around pitchers and instructors for quite some time I am not sure how you are gong to measure this and then how are you going to implement meaningful change.
Well, if you have a pitcher who already has good, quick explosive moves down the mound, you aren't going to create a lot of extra velocity. However, I have kids come to me all the time with this idea of a balancing at leg lift and then presenting a slow, deliberate movement down the mound. Those kids I can make quick progress with.
As far as measurement, I'm trying to find a pretty good study I found a while back. However it was (some help here?) measured time from the top of knee lift to foot strike of a decent sample of mlb pitchers and the correlation between those times and the corresponding velocity was pretty consistent.