Supposedly, Leonard's soul powered the White Knight when he was just a baby. Sure, it was a machine designed solely for war, but every machine has the power to backfire. They probably needed someone to ensure that the gigantic suit of armor didn't start smashing its own people.
The pilot would have the job of guiding the Knight toward its intended target and then sitting back and letting it take care of business. The Knights would fight automatically, but when they were finished it would be the pilot's job to get it back under control.
That actually could make a lot of sense, actually; Leonard and Caesar never use their Knights outside of battle because they don't have pilots. They power the Knights, but after they power it the thing is just a giant hunk of metal that looks for things to kill. It probably couldn't go over small barriers just like the ones in the Dogma Ruins.
We’re not technically traveling through time. The game is running on the Lost-style Daniel Faraday time travel principle of “whatever happened happened.” When the party travels through the Retrospecticon, they’re not travelling back to the actual timeline where everything happened, they’re actually travelling to a separate “pocket timeline,” which is a rough facsimile of the original timeline.
That’s why there’s all these inconsistencies like it being overcast on the day of Cisna’s ball or rainy the night of the attack or why Lucius knows who Leonard and co. are and what they're “famous” for, despite them not actually having done any of it yet. …And whatever the hell’s up with Rapacci.
This pocket timeline exists only for the time when the party is inside the Retrospecticon. It’s created when they enter it and it collapses when they leave it. That’s why nothing they change through their actions carries over into the memories of everyone else around them outside of the Retrospecticon in the present. Whatever happened happened, we’re just experiencing an alternate recreation of things, like the Animus simulation from the Assassin’s Creed games; it looks and feels real, but it isn’t.
Of course, that raises all sorts of questions like “how are they able to bring things back to the present with them?” or “okay, then is the insignia Miu received real, or a duplicate, or was the original lost when Dalam/Valtos/Drisdall died or what?”
I don’t have any answers for those questions. The truth, however, is out there… and by that I mean Akihiro Hino is a giant hack of a writer.
