That would also make sense if she was simply trying to become the new Hyne by merging the sorceress' powers. Really, that makes sense to me considering you have this creation myth of Hyne creating mankind, and then mankind rebelling. Ultimecia is essentially becoming like Hyne by compressing time to a point where only she can exist (no humanity), and she has merged all of the sorceress' powers into herself.

This would make more sense just if she was Hyne trying to undo his mistake of creating humanity.... Though, if she was just wanting to become Hyne herself, compressing time would also ensure that that she wouldn't have to worry about humanity turning on her. This wouldn't have been that hard to include in the game, I think. Even a mention of this possibility would have helped the ending sequences make more sense. FFVIII is my favorite of the series, but I feel like the story does get more and more weak the closer you get to Ultimecia.

I also have to wonder what the SeeD of the future was doing. Was Ultimecia just sitting around in the shadows, trying to pull strings in the past so that she was largely unknown in her time? Based on her speech at the end, it would seem that she had run in with the kursed SeeDs. The more I think about Hyne and Ultimecia, the more I want to actually see what was going on in Ultimecia's time.