According to the GM, plate armor difficulty is "Not too bad", so...
Ambasse Telemna
We have soldiers, but soldiers need protection. We are the Light, so our soldiers must be bright, forever untarnished, unharmed. The Hauberk of Silver shall see to it. Rather like the knights of the end of medieval times, the Ambasse is composed of three layers. All layers are constructed of many differently-shaped pieces, so that any of our creatures can be armored with any or all of the armor layers. The first layer is gambeson, or padded cloth that covers most of the body. This layer is ALWAYS worn, no matter what. The next layer is mail made of steel or Mithril, interlocked rings alternately welded and riveted (or entirely welded [which is better, as welded links are harder to pierce than riveted ones], if made by superhuman smiths). The mail layer is generally sufficient for anything not meant for piercing advanced armor. However, when things become really nasty or you just want to be extra shiny, a third layer can be added. Composed of steel or Mithril plates and fitted over the mail, these plates are basically unbreakable, providing unbeatable protection for the creature beneath them. Because of the modularity of the design, custom-fitted (and thus more time-consuming and expensive to make) suits can be made for important servants of the Light, with delicate lightcrystal glyphs embedded in the plates, capable of causing hostile magic to wash over them instead of harming the suit and its occupant.
Our soldiers tend to have built-in weapons, so our first order of business is making high-level protection for them all. This is geared towards us producing a Thevryn-style smith unit, because otherwise we might get bankrupted trying to armor everything. Although we can resort to only armoring some creatures in gambeson or mail, instead of plate-armoring everything. This will be cheaper. Gambeson should be almost free, but still prevents long-range arrow fire from killing people...usually.
I'm waiting on GM comments on the actual characteristics of Mithril. Depending on said comments, I might make some adjustments to the design.