Here's the answer:
We don't know because we haven't even given it much thought. We're not concerned with unofficial battles as they have no effect on the war. If you want to set up unofficial battles, I'm gonna ask that you keep 'em out of war battlegrounds areas though, so as not to cause confusion. Also, you'll have to host them yourself, because the BAs are gonna be too busy for that.
As far as battle traits go, this hasn't been official discussed so this could change, but the way I think is that if it's a special trait (snap and snatch(?) was one of the ones, I think) where it causes instant death, or whatever other special damage, then you would mention that in your attack proposal and when the BA rolls, they're rolling for that attack. Anything else, generic attacks, you don't have to mention the battle traits - the mod looks all those up before battle.
Anything else?