Too simple Hawkeye. If our empires are capable of intergalactic travel; then they're damn well more inventive then a blade popping out.
Cybernetic prosthetic with a built in mini anti-matter/matter reaction generator in each arm. That should provide enough power individually to get whatever you want done.
I was also thinking an neural-link between him and his robotic arms, and since they're robotic they'd allow for precise control over a technology that rebuilds itself according to the user's thoughts? Think of a rail-cannon and the arms produce one out of existing parts or portal technology. Get rid of it just as easy, and can make something like that. Go ham bro. Don't be a coward when it comes to genocide.