Cosmicdestroyer
Okay, yeah, there’s quite a bit that needs fixing before those would be competitive worthy, and you being teacher worthy.
I can’t look in game right now, but it’s obvious in those two additional designs that there’s is some major issues (a lot of which Kieffer pointed out. You really should read Oneye’s guide).
Reactor Clumping: Wowza, that’s not a good one. Placing reactors that closely is just begging for a massive explosion that will rip apart your ship. You really need to space those out.
No Compartments: Your 2 extra ships lack compartments, I assume, due to the massive amount of crew you have centralized. This is obviously not efficient, nor effective. The guide gives good examples on how to compartmentalize.
Over-crewed: You have a ton of crew quarters. Far too many than needed, assuming you compartmentalize. That alone probably drives the price of your ship through the roof.
Those were just some of the superficial things I saw when just looking at the exterior picture. When I’m home, I’d be glad to take a closer look in game.
EDIT 1:
Okay, I'm home. Let's take a closer look:
Nemesis Destroyer:
Looking at it closer, it has a lot of issues. No worries, they aren't unfix-able!
- Poor Internal Layout: This comprises many issues into one, for the sake of making this list shorter. Main issues are as follows: Over-crewed! (already mentioned). Poor ammo system (You lack enough cannon ammo, and your missiles are all over the place). For instance, missile factories will provide enough missiles for 2-3 launchers, while 1 ammo factory will provide enough ammo for 1 large cannon or two small ones. In some parts of your ship (like on the rear side parts), you only have 2 missile factories for 6 launchers! Among other issues, the Nemesis has way too much extra corridor, no compartments, seems a little under-gunned for its price, and lacks shields. Thrust also seems slow.
Eclipse:
All of the above issues apply, though at least it is shielded and has more weapons. Still, its quite expensive, over-crewed, poorly laid-out, and suffers from reactor clumping and poor thruster layouts,
Supremacy:
As for the Supremacy, it's incredibly large and expensive, thus not really in the competitive range. It seems like it has way, way too much armor though, and the few compartments it does have aren't well optimized.
Overall, there is a lot of room for improvement. I hope this didn't sound too mean - that wasn't the intent. I think they are neat looking ships, they just suffer from a lot of the issues newer players tend to incorporate.
(also, all of your offered ships were above the 200k - 2 million range most often seen in competitive play)
Good luck!
EDIT 2: This post is a bit messy, and long, so I decided to make another one in which I offer you a challenge that will hopefully help you improve!