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Finally, a word on mods/extentions. There are of course a few caveats to take into conideration before using them, which are outlined here if interested. With that health warning out of the way, onto the fun stuff 
w.evans has put together an elegant series of scripts based around improving combat-related AI, found here and here, for in-sector and out-of-sector conditions, respectively. They interlace a bit but they're very modular even within themselves, and there's also an all-in-one-option on the Workshop. Anyway, at their core w.evans has built a system that improves combat AI for NPCs with better skills so it gets special mention here 