No arguments here. I never even paid attention to unit intelligence in vanilla/OXCE. That is why I am very curious how people use it in other mods that they want to transfer this functionality to BAI 
Vanilla AI and BAI work in different way, and Xilmi was the first person to propose migration of native (i.e. modder-set) intel and aggro settings into BAI. What is being discussed here is that, although, approach is overall good, the VAI and BAI intel and aggro doesn't exactly correlate in a way one may suppose on the initial look. Thus, while most units work perfectly fine, others work not as intended.
Intellect = memory function in VAI, while in BAI it is aspect of action fineness.
Aggro = frontal assault vs ambush-preservation of TU's. It is somewhat close to BAI's intention, but now shifted by some amount of whole numbers (in VAI terms) for amount of units, that are supposed to be more cowards rather than brave warriors.
While lacking serious AI tools, modders of vanilla OXCE balance fights by following means:
- enemy amounts, stats&armors and weapons
- restricting X-COM in same categories
- map design and initial unit layout
The proposed solution for BAI to be top-experience is:
- making formulas clear and final
- and then fine-tune aggro and intel settings in RUL files to estimated values either by modders themselves or by community.
By mine understanding, it should be a multiplicator, rather than surplus.
For instance of balanced aggro of BAI = 1, aggro 3-4 for pusher will be enough to represent super-aggressive unit, and 0-1 - 0.2 will be enough to represent super-coward unit. No need for aggressiveness 7-10.
Again, this all being supposed for psychological validity of unit behavior, i.e. player's game experience, and may a bit nerf the overall power of BAI. Which is compensated by unit amount via difficulty level.
Xilmi says that BAI ain't going to be perfect for any mission out there, unless megamod is created specially with BAI in mind. But we can go close enough by hand-tuning.
