I think in an earlier edition there was Armored Batteries that ignored rolls of 5. Not sure why it was dropped or if it would make a comeback. In my experience playing I would rather lose an engine than a weapon, so it would have to be worth more than Armor Plating. Or, it could be worth the same but ignore rolls of 6 (saving a weapon but not a hull).

Someone did this. They costed Armored batteries (no effect on a die roll of 6) at Space Units (for weapons only) *1.5 and Offensive Rating * 1.75. They costed Redundant Shielding (no effect on a die roll 0f 4) at Space Units (for shields only) *1.5 and Defensive Rating * 1.75. I don't know if the Combat rating comes out properly balanced or not.

In my House Rules games, I sometimes use Heavy Armor (Ignores rolls of 3, costs 10% of total Space Units, and costs 2 * Drat), but this precludes the use of Redundant Shielding (making shields invulnerable would have to be very expensive ) and requires that Armor Plating be taken ( you have to have armor before you can make it thicker). This means that you are spending almost a third of the available space on Defense. Level 4 Shields would reduce the Damage quite as much (by 2/3) and usually cost less.