You make some interesting points, for sure. I do wonder, though, if he wouldn't be happier with set at bats ie. DH if it is offered.
It is definitely an advantage for a national league team in regards of double switching if he ends up being able to hit. But DH and regular at bats seems like a real advantage as a hitter (especially a young one) over what basically amounts to pinch hitting most of the week.
The American League certainly would be more dependable.