Yeah, no problem at all. Each ArtDef contains all the model information, and you can also make armor pieces occupy several "slots" by modifying their <Type> (give them several).

I was actually thinking about this before when testing your mod. With so many options for each slot it became overwhelming, meanwhile the benefit of mixing pieces had become basically nil - because each piece gives such a small "speciality", you need a full set to really see a difference in how the unit performs in that speciality.

Oh yeah for accessories, is it possible to force an accessory slot to be something like, ACCESSORY_RING1 and so on for two rings, a necklace, and something else?

True enough just trying to make sure that gloves and helms don't become obsolete by removing (reducing) their armor values and shifting their values to the "suit" of armor.

Also is it possible to re introduce elementium back into the game as an option to blending crystal and metal for what I am trying to do for Champion's armor.

Bascially

Normal ==> Masterwork / Crystal ==> Champion's (Elementium)

I am still not totally sold on making armor out of crystal but the way I have it built now is the closest to the spirit of the game.

I would rather it be set up something like

Normal ==> Masterwork ==> Minor Enchanted Armor ==> Champion's Armor

With potentially a 5th tier in there  for Major Enchantment, I am not fond of the whole armor gets bonuses that get stronger as the character levels, I personally think that armor and weapons should stay static but the individual gets better at using them, like you said, traits.

Anyways that's what I was wondering.

You would do it in the ArtDef xml file, not the actual item files, by simply adding the art from one piece to another. 

Interesting, experimenting around with different things and have found that it doesn't look half bad.  However, there is a downside to doing this.  All drop armors would have to be converted to suits of armor instead of just chest and legs.  Not that I don't like that idea.  This I think has a LOT of potential.  Also I solved, I think, the problem of the non enchanted versions of armor for boots, gloves, and helm.  Leather versions would start at 1 def with a +1 for blunt defense, chain would start at 2 def and +1 for cutting and plate would be 4 defense with a +1 for piercing.  Then make what ever versions beyond that I want to.  One less piece of armor per set makes a lot of things easier.  Just need to finalize what I actually want to do with this mod direction wise.  The version I have posted as far as I can tell works and stays pretty true to Elemental right now, so I will leave it alone.

I'd say a mix is not a bad thing.

Actually the more I think on this the more I like the idea of armor suits being a set for army units and individual pieces being for champions/sovereigns.  Does this sound like an acceptable compromise for equipment for pretty much everyone?  Or should I just make everything available and just make the chest and legs combined?