How should I handle walls, ridges, ditches and crenellations in UA Mass Combat?

@LeonardoRaeleAiming to use UA Mass Combat in Iceshield Orcs encounter in PotA. How should I handle walls, ridges, ditches and crenellations? I'd treat them as difficult terrain and cover – think of each stand as a single creature in the standard combat rules

— Mike Mearls (@mikemearls) February 29, 2016