Luxu is the virus and has been doing his own things already. He restored Strelitzia, and saved Subject X a.k.a. Skuld from becoming a member of Organization XIII. His role is to observe, he is not supposed to do stuff like this.
I think they share a goal (protecting light, opposing darkness), but disagree about the means for achieving it. I believe this to be about determinism vs. freedom, with the MoM representing the former and Luxu the latter.
Yet the only unquestionably non-wielder participant in the war was Saïx. There are some nitpicks (Luxord hasn't yet been confirmed to be a wielder, but is likely to be one; Xehanort doesn't know that Xigbar is one; Repliku is a borderline case), but it looks like Xehanort really was maximizing the number of wielders. Also, why don't Donald and Goofy count as lights? Isn't it because they are not wielders?
It seems keyblades aren't strictly required, but having them is preferred, because they somehow make things easier.