I just bit the bullet and finished off my collection of DLC for GalCivIII. I understand that IV is out but I think this feature would help to improve the realism of both III and IV. As it is in, when tech is researched, the game automatically decides what ship-build mix is optimal, particularly when it comes to defenses. I like shields so I prioritize them with near top-tech shield, and then I went back to research missile defense and suddenly, none of my ships had shields in the ship-build menu.
I think the game looses a bit in the realism and flexibility as, even with high-tier defense technology available, the auto-generated ship-build list can suddenly feature ships with no defensive elements at all. It basically invalidates a good portion of the military tech-tree.
My idea is that three buttons could be added to the top of the ship-build screen, shield, armor, and missile defense buttons. The ship build menu would be populated according to whichever buttons are active. When just one is selected, such as shields, all ships in the list would have shields equipped. If two are selected, such as shields and armor, the defense of ships would be balanced between the two defense types. The same would apply if all three buttons were selected for an all-around defense.
This would reflect both reality. For example, how even while modern fighters are armored, air forces are also rely on active missile countermeasures, sensor jamming, and are seeking to include high-energy lasers to shoot down missiles. Similarly, tanks are equipped with armor, reactive armor, active anti-missile countermeasures, and Boeing is even seeking to develop energy/plasma shielding to harden them even further.
As for sci-fi, major franchises are filled with mixtures of difference defense systems or from special armors, countermeasures, and multiple types of energy shielding.
It may help if defense systems were given their own mass total to count against rather than the overall universal one. This separate total for defense systems would allow players to specialize their fleets and ships more, creating a bit of an arms race where defensive techs and offensive techs are researched according to what competition may be using rather than just throwing as many weapons on a ship as possible and leaving it without any defenses at all.
Taking it even further to have separate mass totals for weapons and utility systems may be good as well.
Each ship would be given mass totals in weapons, defense, utility, or general according to the type. For example, support ships would have high utility mass totals and would be lower in the other areas. A carrier would also likely have high utility totals for fighter bays. A battleship would have high totals in defense and offense, but would lack more in utility. The general mass total could be used for anything and would allow for additional room for customization without a rigid barrier. Also, if someone really wanted to, they could exceed the total for an area, like weapons, as well as the general mass, and dip into the total for other areas, like utility, but at a penalty where some mass points would be lost.