I'd say definitely not worth it, but on the other hand, the dude does dream about a house on a habitable planet. It's not worth it for a mercenary as it would bind him to the empire (and the will of the government) and there would be expectations, if not responsibilities, but it could make gaining land on a planet much easier.
I'm not sure, though, that his deeds would still be enough to earn a noble rank. Much cheaper for the empire to give him another medal, some money, pretty speeches, and a bit of publicity. They might suggest a contract to bind him a little bit. He shouldn't accept any contracts. Maybe if there's a really petty nobility rank, like knighthood, that doesn't cost the empire anything and is not hereditary, it could happen. The empire would lose nothing, but it would bind Hiro to the empire for the rest of his life. Existing noble houses would hardly care about another knight appearing.