Mod requests (orders).

How will Shadya be displayed in Hammers of Fate?
In the original game, she has one texture (red), but in Hammers of Fate, it's purple. If you replace the red one, it breaks the add-on.

No, you're confusing something. Shadya is red, and Ilaya is conditionally purple. I think you're just changing the wrong thing. The textures for Ilaya in the game files are named Shadwin, and below that are files named Shadya. This applies to the textures in the DS folder; there are no such names in the Heroes folder.