Honestly i think it's fine as it is. 5kers aren't exactly fast and even supposing they can thrust, stuff like the Stork isn't likely going to dodge any fire simply because of it's atrocious turn rate. That and let's face it, they're paper. I mean if you really had a problem with getting pirated, fly an armored transport, i.e the Bison and it already makes the Pirates job more difficult - But you do lose cargo. So the trade-off works in my opinion.
I don't believe a large ship should be easy as pie to kill to a lone pirate. If you can't hurt a ship solo, log more. Hire more. Piracy in my opinion isn't supposed to be easy for a single person.