I wouldnt mind helping with setting up a contest at some point
I should still have a few humblebundle keys that can be used as prizes
I nominate Nauvran to start a 'new' such competition. He of course would be free to involve others and also to delegate to himself a less leaderish role once he gets the ball rolling, should he so choose (and assuming he finds someone else to assume the role). I also suggest he start a new thread, perhaps with a link back to this one. Also, if this competition was never properly judged, the first order of business after laying out the 'rules' for the new competition (so people can get started with ship designs) aught to be judging the submissions of this competition, with a prize awarded to the winner.
With regard to prizes, I don't think that cash prizes or anything like that is particularly motivational given the time it takes to build and the plethora of people who might compete. Bragging rights is by far the best prize. What I would suggest is a badge for a prize, something called perhaps "Pirate Extraordinaire", a badge that could only be earned by winning such a competition.
I would prefer a competition that did not require five different designs, but perhaps I fail to appreciate some detail that leads to the necessity. I was also slightly perturbed upon reading the OP's description, that
my own recent pirate design is not, according to him, a fighter but rather a corvette. My pirate does not look like a corvette, it does not fly like a corvette. It is a fighter, albeit a heavy fighter.