Alright, for Rahi. I read your post defending it as an element, but that only seemed to explain the difference between it as an element, and Rahi Control as a power. Wouldn't creating Rahi - creating life - be way too big of a deal for a Toa to wield? Especially since the lines between Rahi and not-Rahi are somewhat blurred, it seems like this ability is way too overpowered as it deals with something that not even the Mask of Life could do.
That’s a very good point. Though this can be brought up about Plantlife just as much, it’s just that animals are easier to anthropomorphise and thus we incorrectly view them as a “higher” form of life. Thinking about how their powers would work in a scifi sense, in which their ability to create Rahi means they take the design of a wifi catalogue maintained by Mata Nui and updated with new species by the Brotherhood, means that theoretically they could create Matoran-level beings if the Makuta created an catalogued such a thing (though I don’t think many sapient Rahi were available for that. Further science-fiction interpretation (sort of violating my “Bionicle is fantasy” post but in a place I feel is warrented) specifies that there is a certain condition of Rahi brains that makes them susceptible to Rahi control, and Matoran and other purpose built sapients would lack it and sapient Rahi either lack it or can go get neurosurgery to have it removed.
I agree that it is a powerful element, but so are gravity and iron which are said to be overpowered even in the original canon. I don’t think it infinges on the powers of the Mask of Life though, since that was literally a death switch for the Matoran Universe to which all biomechanical life was dependent on.