How Was This Supposed to Have Worked?

After the initial Castillo hiring bombshell, I tried to make sense of Andy's thinking.  Clearly he hadn't gone out and looked for the guy who was most likely to succeed while coaching this defense.  If he had, he'd have hired, you know, a guy who knew how to coach defense. I eventually settled on three possible justifications: 1)  Reid thought Castillo could function as a "head coach of the defense" if they signed enough veteran talent and experienced position coaches. 2)  Reid worried about the impact of the lockout on scheme installations and decided he didn't want to bring someone in who would make too many changes in terminology, etc.  And unfortunately JJ's former assistants all have jobs (or had just been fired by Andy). 3)  Reid wanted to put Castillo on the Harbaugh Plan, where a guy in a dead-end coaching job gets moved somewhere else as a transitional step towards being hired away as a head coach. As usual, no one outside the inner circle...