No, the blue shell is invincible to everything until it's about to smash down, so using the super horn item at the right time is the only way to destroy it as far as I know.

You can also dodge it with a well-timed mushroom, but the window is even smaller than for the horn.

I'd have limits on the double switch; either just, say, you only get two; or something more open but still restrictive like "the player substituted must play an inning on defense before he can be subbed out again"

This way there's still a drawback to bringing a starter up to bat in a critical spot: you still have to take a player out, and this is their new spot in the order (unless you want to burn another switch to move them back again)

I just don't think it has enough of a drawback. I proposed it in a couple of Reddit threads but my idea is that when you pull someone out of the lineup, you can "double-switch" them in the batting order with a player already in the lineup, and the new sub goes where THAT player was in the order.