Why would I think they're the Lucavi?

If you snagged the directors edition, check the interviews with the directors. One of them specifically states that the summons were the Lucavi brought back from Tactics. And as to why I find that disturbing, that goes back to Tactics. I seem to remember something about twelve key people called the Zodiac Braves who used the power of the Zodiac Stones to bring the world back to order...

Twelve people, twelve stones... Toss in the way history gets clouded over with a lot of time, add in the fact that the world of FFXII seems to be the same world that created the airships and 'guns' of the city of Goug, and you can ramp up a theory pretty quick here. Toss in some charismatic prat to step in and take all the credit, and you have the makings of an evil church trying to vie for control of the world by forcing puppet kings to take the thrones.

As for my opinion, well, I like to think about the material involved. I also consider the people responsible, their likes, feelings, thoughts, and the way they roll. Matsuno and his team, even though it sounds like they ditched SE during production of FFXII are still responsible for this game, and that means there is a long and complicated history to everything that has gone on. Read the Clan Primer as opposed to letting your eyes glaze over, and you can start to make connections of your own.

Besides that, on the summons front, every game has the summons, and most of them inexplicably have the same summons. Mix it with magic, and... you need an explanation for that?

You're right, you can disagree with the choices being made with the material. What's really ticking me off is that this thread sounds like a Star Wars or Star Trek fan forum thread with people whining about what a company is doing with 'their' series. I may not be entirely clear on copy right laws and the like, but last I checked, the intellectual property rights belong to the company that fronted the money, and to a lesser extent, the people who made the project come to life. That's what I don't get here-it's not my series, it's not your series, it's SE's property. And like I said elsewhere, I really think SE is turning into an EA that makes RPG's.