That seems like an acceptable place to leave off for now and start coding/failing to code things. Plating, surface filth, detailed shading, etc. can wait.
I really like those ships. Their design feel "right", grounded and efficient. Though if you intend to leave them like that, I'd have two remarks:
While they look good, well they don't fit vanilla. I know you don't care much, and that's fine. However you are making a mod, that implies people playing it. If your mod don't fit in the base game, people may be reluctant to play it, and that could be very frustrating. It might be fine for now, if you are only making this for fun or as an exercise, but when you will have sunk hundreds hours of work making a whole faction, you probably will want to see people enjoying it.
Also, I'd suggest to at least completely finish one of the ships. Because maybe you will find out it take a LOT of time to get to the result you want in Photoshop: after all, you talked about blockade runner, armored ships... This is not what they look like right now, and it might take quite some work to get there. Or maybe you will decide to change their size depending of the greebling you want, and you will have to replace all ships mounts, bounds and engines in all ships files. (hint, you don't want that!)
Other than that, this is a great start, and I'm eager to see the result when you are finished.