Momo, have you tried talking to the coach and asking him what he sees as your roll on the team? Part of being part of a team is understanding your roll on the team and accepting it. That doesn't mean you have to sit back and not work at the other part of your game, but if the coach needs you to be a PO you need to accept that that is your roll on the team. Depending on how your coach structures your practice you maybe able to take some reps in the infield or get some BP in. You need to use those times to demonstrate to the coach that you can handle a two-way player role.
Im having trouble wrapping my head around the Varsity A and B teams. Why not have have 5 Varsity teams so everyone can make the team an play? Where does it stop? My sons played in a larger school in a major metropolitan area. All of the schools in our league have large populations. Most have a Frosh A&B team, Soph team, JV and Varsity team. The Varsity and JV teams are combined into one team. If you do not get significant playing time during the weekday and Saturday V games, you are on the JV roster and play in Game 2 of the Saturday double header. Game 2 does not count towards the standings. There is a pretty good drop off of baseball talent between the V games and the JV games. I could not imagine diluting the talent even further.
In NY, from what I recall, you can not go back and forth between varsity and JV. I believe that once you’re called up to varsity you must stay there. But I’d have to doublecheck on that.
The why? As I said above, it’s often parental pressure.