I think Scratch strikes a reasonably good balance. Some of the others definitely dance a bit over the 'too clever' side of things.
Animal thoughts wouldn't come across to us as "me want food" or things like that - that's a broken language trope and implies a creature attempting to speak a language they don't know well; it wouldn't fit for animals who are not affected by any spell and aren't trying to speak our language. Their dialogue should be simplistic, but still clear - their minds work well enough for being the creature that they are.
In terms of unexpected consequences... the real one that you'd have to consider is that Speak With Animals functionally broadens the field for the Hakrness test considerably...
