I like this. I truly like this. And this is as close as we can get to common enemies who personify the 'Light is not Good' theme without pulling out another elaborate process which would lead to an exclusive 'Light' enemy species while finally dealing with the morally grey area of being Nobodies all in one fell swoop. And yes the concept of a messiah who intends to bring salvation to the Nobodies is a concept I toyed with a lot. KH2 tried to do it, but I don't think I'm alone when I say that I don't feel it. :/
Hmmhmm, and if these Light filled Nobodies would go down the road of going against anyone with darkness in their hearts, no matter how small, it makes sense. They don't understand that hearts need to have a balance because they don't have hearts in the first place.
My opinion differs though. BECAUSE most Nobodies don't have hearts, they really should not get a full pass and get to live with society, nor I don't think they are able to. Having a heart means emotions, and emotions means having a conscience. Nobodies, no matter how sympathetic their plight may be (and Sora still has not even grasp their tragic existence) just cannot understand that their actions can hurt other people, nor would they care. I think at the end of the day, Nobodies will end up at the opposing side, even if a protagonist reaches out and attempts to rehabilitate them. Yen Sid is right when he says that they are a threat, the only thing wrong with his viewpoint is not giving a reason behind them being a threat beyond "GRR THEY ARE SHELLS THEY ARE NOT MEANT TO EXIST KILL THEM KILL THEM ALLL!!!" Yes all they want is an identity, but not having a heart automatically means they'll use the easiest route to get it, and more often that not that easy route is the wrong one. Even if a Special Nobody becomes a spokesperson for them, his or her argument won't have much basis because Special Nobodies tend to HAVE hearts (see Roxas and Xion, though we have no idea what Namine actually is.).
This is assuming though that we are sticking to established rules in the KH universe. I've always found the concept of Nobodies not having emotions and thus a conscience fascinating so I tend to stick close to that rule.