I'm not sure I understand. If the core AI code is not available for modders to change, then how can it be that tweaks to AI weakpoints were made? And is there a reason this isn't possible for Vanilla?
There are ways to change the game in other ways besides how the AI plays it to try and mitigate its weaknesses. For example, the AI can be inefficient in how it uses the black market, so we give it a reduction to purchase prices.
The way we went about doing it involves some things that are not present in the original game, so it only works with E4X compatible mods.
It would take at least some about of manual effort to port this to vanilla.