Sure, the cockpit is open to a shot. But that seems like the ONLY place (at least from the picture, I have yet to download it) that isn't armored (perhaps the engines too, I'm not sure). You could just modify the ship slightly, and save yourself some grief. But in reality, unless its a smart missile, that single area of weakness is going to be hard to hit from any range > 500m. And with your stated intention of using it to draw fire from more expensive capital ships, I'd say this isn't a bad design, assuming its fast.