If a player has power, they have power. A player’s power is not determined by the handedness of the pitcher.
I think they need to make vision and/or discipline based on the handedness of the pitcher. If a player can’t hit homeruns off of lefties, it isn’t because he suddenly lacks the strength to hit the ball out of the park. It’s because he can’t pick up the ball out of a lefty’s hand.
Of course with switch hitters there still should be a left/right power attribute.