That kind of thing would make small ships even more useless, though.
The point of the primary armor is to give every ship a half-decent amount of ability points.
Big ships can add a few more ability points, and get more heavy armor too.
A ship's value in combat is on the order of (Weapon power) x (expected hitpoints)
IMO, its not about damage reduction ability. Its about Keeping your ship operational as long as possible:
- For individual ships, that means using lots of the heaviest armor available, along with a strategically decided amount of advanced armor (the smaller the enemy weapons, the more you want)
- In big fleets, you want the other allied ships to have light armor, so they draw more fire away from your important ships ... at their own expense of course
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That's assuming the enemy targets the high-hitpoint ships first.
If they're targetting the low-hitpoint ships first, then you've got to adjust your strategy... Lots of smaller ships with light armor, and your bigger important ships with medium armor so they have decent protection for the end of the battle and enough hitpoints to not be targetted first.
Now, if you're attacking in overwhelming force, you might decide to just go with heavy armor all around. That way you lose a few ships, but the survivors aren't crippled, and are quickly repaired.
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The advanced armor is just icing on that cake to multiply the effect of having lots of heavy armor.