That seems very complicated. The "best" option, in my mind, is use a total for fielding for all coaches. If the 1B coach sees a flaw in a player's throwing motion is he really going to keep his mouth shut?
For pitching, it's BC, PC and BU.
For hitting, it's BC, HC, 1B and 3B.
Very simple. I think what would happen is that the current FI are coveted as BC. But, if you miss out on that elite 85 fielding rating BC, you can "make it up" by signing above average fielding ratings with other coaches. Instead of that 85 PC, 7 FI, you could go with 79 PC and 28 FI. It would open up the options and the guy that gets the 55 FI now won't feel like he got screwed in the fielding department.