*shrug* In EB1 I pretty much standardised the modifiers based on general area of origin and culture (ie. how familiar the troopers could be assumed to be with difficult terrain and bad footing), weight of armour (heavier armed men aren't as nimble as the light guys, and the extra mass of the gear on top of the body weight makes for more problems on soft, slippery etc. ground), and density of formation (closer ranks are distrupted more by trees, rocks, crevices and whatever, and warriors used to fighting in closed ranks will probably be feeling somewhat isolated in the more open formations required). Used a roughly similar approach with the snow modifiers; people haven't been complaining, from what I've seen, so it seems to have worked out well enough.