As far as I know, there is no specific "AI" file in SH3, but rather the AI behaviour -encoded- is finally modulated through other aspects -modified for good in GWX and NYGM- like: Sensors, visibility, etc.
So I'm afraid it is a large amount of stuff you would need to port.
But if you want to improve Destroyer behaviour with no frame rate loss, then take a look at CB's site:
http://www.ebort.com/
Hope that helps