In "Stars!", you had the concept of miniaturization - older tech cost less and less to make the more you exceeded its tech-level requirements, making it so using the newest tech was not always the best choice.
I saw a suggestion on this forum that you could use this mechanic in GalCiv3, but have it be different for every civilization - one would make every component better armored over time, one would focus on increasing damage, another would decrease space requirements, etc.
Good idea, so I'm posting it here, since this is something you should be able to choose in the civ editor. Maybe you could spread the points around in 10% increments, so you have, say, 70% Damage increase and 30% Armor increase.
There are several game mechanics you could base the efficiency increase on:
- Research on related subjects, like Laser III giving +15% efficiency to Laser I modules.
- Some "private market" mechanic, where efficiency increases are awarded semi-randomly according to economy/research stats.
- Number of modules produced, with glitches fixed according to customer feedback.
And of course, some civilizations would gain efficiency faster than others, depending on the abilities they purchase, wonders they build, etc.