Now in my humble opinion i believe that Rinoa cannot be Ultimecia due to the fact that Laguna tells you that Ultimecia lives so far in the future that none of them could still be alive.
My theory is that Ultimecia is a descendent from Rinoa,actually i believe that Rinoa and Squall are the great-great-great grandparents of Ultimecia, and that´s why she´s a sorceress!!!!
As to her first name it would be a pretty common name, and she changed it after rising to power...just like so many warlords!!!
Not a bad theory if i might had.
