Alex...
I like these scenes you get several large buildings destroyed and your going to have a huge debris field upon which troops and AFV's have to navigate. You don't send in the dozers to clear a path then send in units so, for me, its a gritty picture of urban combat
When you develop the groundwork how deep is it? I use cut and shaped polystyrene as a bulk then add brick rubble etc as a fine layer. I have a friend who does large dio's like your self who builds up the level with real materials and uses masses of rubble etc. Just wondered what your method was
Mitch