Rather have Tait than Caba, though Crawford and Caba are probably a wash.
My breakout candidates:
Johnson, 2 years from TJ
Abel, doubt he's totally lost it.
Mendez, has the eye to hand coordination, fix his swing and . ..
Nori, same, fix his swing to get more pop
Graves, frame and age where a jump in velocity could result in a big improvement
I'm not sure you can teach a young hitter how to hit breaking balls or develop real plate discipline, I suspect a lot of that is innate, the ability to see spin and the eye to hand coordination to adjust in real time.
Same with command, most of those high velocity/poor command pitchers have failed to improve.
Command is probably related to another innate talent, body control, which relates to consistent mechanics and not developing a "tell" on some pitches.