I appreciate the sentiment and thought about placing the "plate" umpire some distance being the catcher. I see two main obstacles:
1) given the skill level and lack of practice of many of our kids, the number of passed balls and wild pitches would require the umpire to be doing a dance most of the game. Staying out of the way of a catcher scurrying to retrieve the errant ball would be almost impossible. That also discounts the need for full gear. In a normal stance, behind the catcher, I feel somewhat protected. Anywhere else, I become part of the play.
2) the number of times that a call needs to be made on a shot down the 3B line is minimal - probably less than 2 or 3 times a game and that includes fly balls to the outfield. The perception of coaches of us hanging out behind the plate would inevitably call into question why we don't just assume our normal position. That's a discussion that I won't have.
I've asked our supervisor the same question and we've spent hours having this discussion. In the final analysis, I think making calls from behind the P is the most sensible.