As a person who has opened up a few xbox controllers to clean them up ‘to the max’, it’s probably beginner level DIY to open it up and disconnect the rumble motors. I think it was even broken in one or two we had ( OG xbox and wired 360 versions), and the system doesn’t prompt you to do something about or, or refuse service (can you imagine? that would suck). Still, I’d try to disconnect it non-destructively first