TrackMan does compile stride information for us.
I can see how stride speed might relate to velocity. On the other hand, you could say stride speed would relate to more power and bat speed in a hitter. The problem is all actions should be under control. They need to be fluid and repeatable. Timing is most important.
Now if a pitcher could maintain his mechanics, throw exactly the same, and still add some speed to his stride, without losing balance, I suppose he might gain some velocity. Much like the velocity an outfielder might gain by crow hopping.
Not sure that simply timing the stride would tell us much. A 7 foot quick stride might take longer than a 5 foot slower stride. Maybe there is a way to actually measure body velocity. Combination of length and time. I would only trust some type of mechanical timing vrs. Hand held stop watch. Hand held just wouldn't be accurate enough in this case.
The thing to keep in mind is there is always a perfect point that is individual to any pitcher or hitter. Anything below that will disallow maximum production, anything above that perfect point produces failure. So one has to be careful. Most successful hitters and pitchers operate slightly below that maximum line. Because going over it most often produces failure.
For the record, I am for gathering as much information as possible. I might be old, but over the years it has been proven how important any and all information can be. I just don't believe in the proverbial magic bullet. It's always a combination of things and that combination might be different from one athlete to the next. To me the best pitching coaches make adjustments rather than change what is natural. I have seen young pitchers from one year to the next, go from being smooth and effortless and being a prospect based on natural ability... to looking like a robot throwing a baseball and no longer looking like a prospect. All instruction is not good instruction. The number one ingredient is always natural ability. The best pitching coaches can do wonders with the kid that has natural ability. The bad ones can actually destroy that natural ability.