Actually, I see little evidence you can teach command, how many bad command prospects become average or better after a few years in the system. Very few if any. From what I've seen, more prospects have substantially improved their velocity v those who improved their command. That's because just like velocity, body control (the ability to repeat your mechanics consistently, the key to command) is an innate physical characteristic. Note that almost every pitcher on the ML roster has average or better command.
Minimum velocity is important, very few pitchers are 3+ WAR if they throw under 92 MPH, Ranger being a notable exception, and at his best is 92-93. Nola at his best was 92-93, t95. The problem with 92-93 pitchers is they have no margin for error if they start losing velocity (but that's usually a contract extension issue).
Once you get to 92-93, additional velocity has less value than other attributes, because self-selection over the last decade as average velocity increased means more ML hitters can hit 95-100 MPH FBs if they lack spin and/or are badly located, Luzardo being a prime example. The elite pitchers throw 95+ but also have the complete package of skills. The rest are a tradeoff between velocity and other attributes.
So to me, you should focus on both minimum velocity (can a prospect reach an average velocity of 92+) and functional command (does a prospect have the body control to develop plus command?).
For older prospects/rehab projects, assume you can't fix either unless there's an obvious mechanical flaw.
With these players, "breakouts" usually come from adjusting grips/teaching new pitches, say dumping a bad slider for a cutter or sweeper, not improving velocity or command - what you see is usually all you're gonna get.
