I think the game could benefit from a system wherein in the aftermath of a large battle you (or whoever owns the territory where the battle took place) would be able to "recycle" the usable parts of the wreckage.
What I mean by this is, the game could implement a feature where if a fleet is a certain size (determined by number of ships, or the sum of the cost of all the ships in the fleet surpassing a certain value) you would be able to construct a building to sweep up the usable bits of the wreckage to add back to your own supply, but it wouldn't encompass the entire cost of the fleet(s) involved in the battle, maybe only 50% or so is recovered, and the size of the "mineral deposit" would be determined by of course the overall resources available in the wreckage and a certain time-span to salvage it all. So for example say the sum of the minerals worth of ships in a battle for both sides is 20,000 minerals. Both sides take considerable losses, and there's 15,000 minerals worth of dead ships floating out there. Well 50% of the dead ships are still salvageable, so that leaves around 7,500 minerals total in that deposit available to be recycled. You could make it so it would take a certain number of years – or even months if you wanted – to clean up all the debris left behind and it would add to your monthly mineral generation, and after said certain number of years or months, and the number of minerals generated by that specific deposit was equal to the number of minerals usable in the debris it would disappear and you would have effectively saved yourself some minerals. You could also implement the "research" aspect into this as you're of course gathering things left behind from the enemy fleet as well, so it could give bonuses to that or just add percentages to the tech researches.
Hopefully this all makes sense! If you need help understanding this, feel free to ask me in the comments and I'll attempt to help explain it better, but maybe someone else will beat me to it.