We know that enhancement bonuses increase the armor bonus:
Enhancement bonuses to armor or natural armor effectively increase the armor or natural armor’s bonus to AC.
… and armor bonuses normally don't stack. Chahar-aina and Dastana are exceptions to this though:
Chahar-Aina: This “four mirror armor” can be worn over certain other types of armor to provide an additional armor bonus that stacks with both the foundation armor and any shield worn.
So, how would enchanting all three pieces of armor work out towards one's AC?
Best Answer
Only the highest enhancement bonus applies
The Dragon #318 article "Oriental Adventures Update: Eastern Flavor" on Magic Chahar-ainas and Dastanas says
Note that the Arms and Equipment Guide represents the dastanas (15), superseding Oriental Adventures, but changes little except putting the dastana into the Shield category exclusively (rather than OA's Shields and Other Additions category). The chahar-aina remains exclusive to Oriental Adventures.