This is always the hardest part of game design. Make the rewards to easy and they lose their value and the game itself becomes dull and the player population moves on. Make it too difficult and the game becomes frustrating and the player population moves on.This limited rare wreck seems like a good concept, I'd love to get my hands on an original 300, but it also ties into the pay2win argument. If your definition of "win" is getting a limited ships like the one you mentioned (it is for me), those with little time will probably not find it, and will have to buy it off of the person who could spend 24/7 to get it, and then put it up for sale for an exorbitant amount of UEC. Thus the player with little time, but probably a thick wallet, could buy it with real money. Thus I would "lose" , cos I probably won't have enough time or money to get it. I'm not saying this is necessarily bad, it's like real world economy or like EVE, but it still makes me a bit sad lol
There needs to be a progression of difficulty with the upper limits being hard and only really achieved by a small percent of the players. Luckily within SC even in an Aurora or Mustang, you can still participate in most of the game and contribute to the cause. Even more exciting is the fact that you don't even need to own a ship to play and be a valuable member of the team as you can be a Marine or ship crew. And this I have to say I am really looking forward to seeing how it plays out for its something unique in the market.