The point of adding SMBS levels is to be able to play the original SMBS but on a smoother platform with better graphics. We probably won't be "improving" the gameplay just because some things are a little odd. Because the Icicles never had the formation animation and didn't respawn afterwards (as far as I know), we likely won't be adding that functionality to them, since that's not how SMBS actually works. As for the Sidesteppers, it is an interesting idea since that's how they behave elsewhere, but since they don't behave that way in SMBS we probably won't be changing them. From what I've seen, the Barrels and Trouble Bugs (that's the fireball, right?) are identical except that Barrels can be destroyed using the Hammer item. I suspect we'll probably make the Barrels armored (like Buzzy Beetles, Spike Tops, and Bullet Bills) and the Trouble Bugs outright unkillable (like Firebars and Podoboos). Good catch. I guess the easiest solution would just be to remove the bottom coin block. We'll definitely be looking out for other such things.