aka: You really want to use derelict ships for whatever reason and just want to handwave it away.
Right. Do you have any idea how many ideas there are that you take for granted in AI War that started this way?
I say that in jest, kinda, but honestly that's sort of the nature of this sort of thing. I needed a plausible reason for the AI to not just crush you, so had to invent it being distracted. I had a mechanic that needed to have some sort of lore attached to it, so lore was conjured-up.
The Neinzul as a race came about because I wanted to explore a mechanic where there were perpetual children through attrition. So a whole race popped out of that. The nature of the spire as a species came because I was playing around in Zbrush and came up with a cool visual style with the white. So then I came up with some reason why they would look that way. I also was able to cheaply make really large ships with that style, so hence them becoming the most powerful race.
If you're a AAA studio then you can just make things out of whole cloth because you thought of it, but for me I've generally had to take ideas in all sorts of random orders, often because "hey I can do this thing, so how can I make it fit?" Or "hey this art would look cool, what can I do with it?"
Change for the sake of change? I honestly have no idea.
It's really very simple: I have a cool way of doing the graphics for destroyed ships, and I think it would look dramatic on planets scattered around. Thematically it would also be fitting with the wreckage of past wars (which is what the scrap piles were in the first game, too). People also have really latched onto the name of derelicts, because it just sounds nifty.
Frankly I don't really care that much beyond that, but I think it would look cool as heck. These were in the spec from day one on the first KS and nobody complained.
The repair mechanics on these is simply so that the AI has a way of denying you resources (as with metal harvesters), but you don't have to expend metal to get metal, as that previously led to slow doom cycles of annoyance. There are a few other mild usability features that get smoothed out with this, too. Visually it would work with any of these approaches, even with metal harvesters if we wanted to make those free to build but just take time, or whatever the case.
Overall it doesn't really matter a huge amount, but visually this is what I have a cool idea for, and I think you'd enjoy looking at this more than anything else I can think of for this thing. That's really it.