I'm still not convinced it's a major inconvenience to be a LH catcher. The field is basically symmetrical from that position, particularly given that your most common throw by far is to 2nd. It's not as if right-handed catchers have a particularly hard time throwing to either first or third, so it really shouldn't be an issue to be a lefty. The main thing is that for throwing out baserunners it's best if your throwing arm is away from the batsman, so more right-handed batters means it's advantageous to be a righty. But that's not a very heavy weighting, really. With all the switch hitters in baseball these days, there are many teams that are lefty-heavy against right-handed SPs on a regular basis.