But not body types or shapes.
She shares it pretty closely with Dogs (...obviously), Wolves, Cats and Rabbits
Long thin arms, short tube legs, cylindrical body, approximate height. There's a few more subtle differences in body shape (seems like the rabbits are a bit more wide, cats are a bit thinner, for rexample) but you could slightly alter those proportions without erasing who the animal is and without full animation overhauls. would, however, need a new falling animation since covering her skirt is a bit hard when one does not wears bottoms
In theory, anyway. I doubt they'd go with this idea since they'd need to leave some of the more popular types (hamsters, frogs, birds...) and you'd need to pick the top 1 or 2 neighbords per naimal types you DO pick. and it's a bit more effort on the costume front than just color swaps (would need new heads, if nothing else).
IMO if they ever went with an Isabelle echo it would probably be Lottie
She kind of fits Isabelle to a T the most of any other character. She even has a skirt and a ponytail.