I like to hire my assistants for a specific role, but that isn't always possible. Last year, I had a hitting coach (student teacher, former player at Valpo), bench coach (veteran teacher and baseball coach in the area), and an assistant (former player at the school from years back, in charge of scouting and field issues). Tough to find good help, but I think that assistants must compliment the program while implementing the program. I expect my assistants to understand our program philosophy and to use it in everything they do.
I also think every assistant needs a role...something that they take a personal stake in. Doesn't mean the head coach doesn't oversee the role (depending on the experience and background of the assistant), but I think every person, player or coach, needs to know what they bring to the team.
Anyone that is willing to be a volunteer assistant should be appreciated and well taken care of...it is a tough job with no pay. Great assistants can make a huge difference, though....I wish I had more good ones to go along with the group I already have!