Be careful: are you trying to predict legal results, or find truth? Those are (unfortunately) rather different questions. If you're looking for truth, you don't care about what makes "powerful imagery for a jury".
BTW, the "carbon fiber hull fatigue" theory is not GPs, it's the extremely obvious top candidate for the failure.
Anyway, there is still no evidence that using a gamepad had any concrete negative effect. Letting passengers drive? Yeah, that's a problem. But it would be at least as big a problem with industry standard controls, which wouldn't even have the faint advantage of familiarity.