I feel like a kaita can be formed from any three Rahkshi. As such, there would be many more possible kaita than those you’ve created here.
That being said, the ones that you have created have really good powers, and they really make sense with the original powers of the individual Rahkshi.
One of the things that made the set forms of the kaita neat was the unique body shapes. I would be really interested to see even more crazy builds for these kaita. If the sets existed, of course.
The Split Body would be really cool. Maybe change the power so that it only splits into three parts, and then give the set combiner three-way symmetry and the ability to split.
EDIT: Wait a second, a kaita splitting into three parts is just splitting the kaita back into its components. For it to actually have an advantageous power, it would have to split into more than three parts, as you originally had it.