It would take a huge amount of research to figure out how all the ratings come into play for the different roles. PC is easy because one rating seems to be of overriding importance. Go through a bunch of teams using a variety of parks, record C-ERA and PC rating for each catcher on those teams, and you generate a reasonably accurate correlation that will become more accurate as sample size is increased. In general, each of a team's catchers is likely to play with similar effects from pitching staff, park, defense and opposition. Doing it for coaches would require the coach's main rating along with Patience, Temper, BC rating, and possibly others, all with unknown importance of each secondary rating. You'd then have to correlate it with development, which would be significantly different for each level/franchise/season. A MiL coach for a franchise that has had multiple top-five draft picks and an owner who likes to deal veterans for prospects is going to have better results than a coach of a franchise in the midst of a long run of contention with a lot of veterans that trades away some of its best prospects.