I'm just focused on starting pitching right now. Signing big expensive arms for contenders can pay off, though... at least recently -- Wheeler, Verlander, Gausman, Scherzer wherever he goes... GMs just have to either be smarter or more lucky in picking the right ones.
But you're right, the Sox always have a better history in trading for #1s or #2s. I loved the Boddicker trade in '88, which helped Boston win two divisions... in 2 1/2 years, he earned 11.4 WAR -- and all for rookie outfielder Brady Anderson (who I liked better than Ellis Burks at the time) and a prospect named Schilling. Moon would say this is the main reason you need a deep farm in the first place.
BTW, I love Castillo, but Seattle traded its #1, 3 and 5 prospects (and another arm) for him... that's the equivalent of Bloom swapping Mayer, Rafaela and Bleis -- for one guy. Unfathomable.
As for developing a staff of homegrowns, this is where patience with call-ups is most important. Pitchers are always working on learning new pitches, and coaches and/or legends like Pedro need time to teach them. It's much more common for a pitcher to change than for a guy like JD Martinez or Justin Turner to totally overhaul their swing, and strike gold.