To absorb (all?) time and space, becoming the absolute power in the universe isn't her motives it's her intent. We aren't really given much insight into motives during the game but I think we can safely say that she does not want to be the only thing that exists forever, she has no choice. SeeD are going to kill her and she knows it. I'd say self preservation is a good motive here. Who can't feel a degree of sympathy for a person who just doesn't want to die?:mog:
All black waltzes, could have easily been Vivi or one of the mages that live in the village. The game is full of sympaty for black waltzes and black mages. It oozes it.:mog:
But this is interesting. Though is Ozma really a villain? You are warned to stay away from it, then you are given a chance to leave it alone before it attacks. It might be better thought of as a wild animal asleep in its nest that you disturb and frighten rather than an intelligent being with motives.:mog: