And Rig, for marching, is the animation gonna be different were the soldier has his weapon slung over his shoulder or carrying it from the butt of the weapon?
We don't really have an animator(besides Azrooh, who has limited time) so there isn't much we can do with animations at the moment. We may do away with marching completely and change the system to jog/sprint instead of march/jog. Having all three would be nice but it really all depends on what is possible. In any case, I doubt a weapon-slung-over-shoulder animation would translate well into a shooting animation, or really anything else.
Just curious and I don't know if your the authority on this, but how would events be set-up? Because lines obviously wont work so I'm curious to know how formations will go or if its just gonna be everyone over the top.
It's really up to the event hosters on how they their regiments to fight. People have talked about simple squad battles, basically just line battles without the lines, people move and fight in loose blobs. There are tons of other ideas that were put up. Ideally, when the mod is released, there will be different events to suit different tastes.
Just curious to know what will the sappers (or Engineers) be able to build in Iron Europe different than the constructions of NW and NaS? (Like Trenches, barbed wire etc)
I don't have a solid answer for that yet. Personally, I would rather just do away with most of the building and limit it to digging small mounds. In NW being able to create fortifications comes in handy, but in WWI, where most of the maps already have trenches and bunkers, I don't really see the point. But that's just me.