I guess a summary of what Im gathering here would go something like this:
It would be foolish to spend large amounts of time strongly focusing on one just training tool. Spend the majority of your time training on the track running high quality sprints of various distances. And use things like squats, sit-ups, core, stability, mobility, coordination, conditioning as supplements toward your speed training.
Thus, have your entire program revolve around speed. The squats can help me get faster, as can the core exercises… but really, the vast majority of my time and energy should be spent running.