Could Scotty have locked onto Khan's signature and beamed him aboard the Enterprise? I could swear that has happened before on one of the shows.
shareWe saw what he did to the Klingons in Into Darkness. Imagine a wrath fuelled Khan on the bridge!
shareYes and no. I feel like the rule is that shields have to be down first. So, they'd have to strip the shields off of the Reliant, but additionally, they'd have to drop their own shields to beam Khan over, which would be risky. Also, beaming him directly to the brig would be fine, but if they put him anywhere else, they'd have a genetically-modified super-man on-board their ship. This might result in big problems; the last time Khan was aboard the Enterprise, he almost took it over - and that was when he didn't have a personal vendetta!
I might have that shield/transporter thing wrong, but that's how I remember the "rules" work. (There might be contradictions/exceptions, too)