I seriously considered putting down the Occuria as an option, but I decided against it because I wanted to limit it to single individuals, not entire groups of people. Same reason I didn't include ShinRa or the Yevonite clergy.

So part of me agrees with you, but then again, you can always take a step back and find another instigator. Yu Yevon would never have created Sin if Bevelle hadn't attacked Zanarkand, for example, so are the leaders of Bevelle the "real" villains of FFX? Or, again, do you need some level of intent? (I know it's not a direct comparison, since the Occuria were more involved in the events of FFXII, but it was Venat who chose to act directly through Vayne and Dr. Cid, which I think makes him more culpable than the others.)