It will. *cracks fingers+knuckles* lets see what I can do, once I finish the other stuff im working on.
Hold on, a thought that might make your job easier.
From what I gather, all art (as in, the ones in the gameplay) are already dictated by promotion: specifically, racial promotions. It's why generic units look different between elves, dwarves, demons, and dwarves. Art is most likely already dictated by promotion already, with 'human' being the default setting (and having no promotion).
One solution might be to create a new promotion (3, actually), based on alignment. Coding would probably be similar to how units get state religion assigned to them for purposes of Infernal/Mercurian spawning-after-death, only 100%, so that all units have it.
While you could code it so that every unit checks what the owner's alignment is every turn, that would be a drag on the system process. Instead, a beginning-of-turn check each turn would provide a single A/B/C as to what the current alignment is, and if different could activate the process accordingly.
I'm not sure if you could get the coding to work like this, but one avenue to think about is the Military Adviser function. The Military Adviser already has the coding to find and signal all units or certain units the player can see on a map. If you could use that coding or identifying all units yourself, you could implement something like a group promotion action (when you have a lot of promotable units in a stack, IIRC you can promote them all with the same promotion).
If you could do that, your coding could be much simpler and more effective than a unit-promotion-based changeover that occurs for every unit, every turn. It would be something like
Is -alignment- same as -stored alignment from previous turn-? Yes (stop)/No (continue)
If Yes, what is alignment? Good/Neutral/Evil
If Good, Military Advisor mumbojumbo "Select All Units", remove Alignment Promotion, Give Good Promotion
etc.
If I were still programing, that's what my first line of enquiry would be.