Problem here is that you are saying OP can't ever serve 125 because you couldn't. Then of course, the question.....what does YOUR serve look like.
You base you view on YOUR serve. I'm just asking, is your motion as good as OP's?
If it is, you have the POTENTIAL, just like OP, to serve fast with direction. Now if you go out and break your spine tomorrow, you will not reach that POTENTIAL.
But if you worked on your serve 3 days a week for say....4 years, had coaching, was a natural athlete, it's entirely possible YOU could hit a 125 mph serve... IF you had a motion as smooth as OP's.
It starts with smooth and ease, then you gradually increase the pace. I didn't mention anything close to Roddicks, Raonics, or Ivo's serves.