For the following reasons I believe Bosch should become a Reserve Deputy for the Los Angeles County Sheriff's Department:
1. Because they do not have an age limit.
2. Because Harry may not need academy training or just need their low-stress academy they offer reserves.
3. Reserve Deputies (RD) can select what type of work they do and that includes working within the Detective department.
4. RD can work anywhere within the County of Los Angeles.
5. RD work entertainment and sporting events.
6. RD can make 60k plus per year working part-time.
7. Harry's former partner Jerry or other officers in prior books can work with Harry on new cases.
8. All the above make for an endless number of potential story-lines.
You can review the details of Harry's new job at the following link.