I'm shocked how we don't have an Operator based on the Luzon bleeding-heart dove, it's SUCH a dramatic bird that could be made into such a peak design. Also I'd love to see someone based on the shimaenaga. I have a shimaenaga plushie. Gurney’s Pitta, Greater Bird of Paradise, Blue Jay would also be great. Damn, that's all birds.
Me and my friend have long wanted a tanuki Operator.
Also I'd want more fish, they're so colorful and diverse. Shame the Aegir designs don't reflect the prototypes that much, we need more fish-y elements.

Mostly I just like it when I see an Operator and go "damn this is a cool way to rework the animal into the character, I can totally see it!" whatever animal it is