Well the whole concept of the Nova Guyver was to see if it was possible to incorporate the power of a star into a Guyver. Now as for the twins, yes their abilities are a direct opposite of Black Nova. Where as Black Nova's powers are more gravity base and incoporates the destructive power of a black hole. Well with the re-writes, you are going t see some changes, but also in some of the more current fics you will notice quite a bit.
Now the change that the Nova Twins will have....You got to wait and see. I really don't want to put to much out right now, because with the rewrites I"m going to do, it's going to explain quite a bit and with the current fics that are going to be coming out (I don't know when) you will see those after effects. James is going to be helping me out and thus will be doing some of the current fics.
I know I only answered your question vaguely, but like I said, I've read through my older fics and see that I left out quite a deal of information that I, you guys and even James saw that I needed to add. So things will be explained in more detail. I plan to have more character development, which I like doing. FIGHTS!!!! will be more descriptive and as all you know, hand to hand combat are my guys forte'.