For Sazanka, I don't count her because, while she does seem to be a nice girl and one that would be good for Cayenne's rough exterior (which is what I think was really Shrade's point), she and Cayenne are an afterthought to the plot and not nearly as important as Shrade and Cayenne's relationship. I was focusing not necessarily on couples (Kagura and Mikono are not a couple, after all) but simply that there is an apparent overlap of powers between characters who have important connections via the plot. (Which, if we add a bit more to it, brings up some further differences to Amata and Kagura. Their powers are utterly nothing alike... you'd think if they had some past connection that, maybe, their powers would be somewhat similar.)
As for Zessica, I don't know how similar her power is to Amata's because it seems to change every five or so episodes (
or its just getting more vague as to what the hell it does) but you may have a point in that they both project an action or some such. Fudo does describe both of their powers as reinforcers of sort: Amata's gives flight to the Aquarion, Zessica gives strength to the Aquarion. But this is rather off on a limb for now...
As for Zessica's simmering jealousy, I've done retrospecting, and I think it actually may make sense as to why its being dragged out this long.
Our last person with abandonment issues? Its Zessica. (It was played up with ghosts before and with Mikono later for when they were in the dark, but think of her character: surrounds herself with friends and is quick to make them, keeps her insecurities a secret from everyone, puts up a strong facade, these are all classic symptoms of abandonment issues. Weren't you the one who thought that she may be all alone in spite of having all those friends around her? Her one episode preview narration is about her hidden heart...) Why doesn't she do anything about Amata? Because she doesn't want him and Mikono to leave her behind and be rejected. If she keeps quiet, she can remain friends with them. Make matters worse, Amata is the only person we've seen her trust her insecurities with in this show and, now, she's in a position where she could lose that if she says anything.