I'm afraid I'll leave the development of Mercenaries all to you. I am going to give you the max file with the models and I'll teach you how to bake shadows. It's easy but will take render time, if you're up to it. There's not much you have to do just import the models you have in your map to the scene, (the light is already set) and bake the textures for the models. From there you figure it out how much you want to compress the shadow maps, remember it can go as low as 128px.
Edit; Whole scene might be 2 or 4 Megabits in total so you'll have to remove the other models but you'll have a really good optimization and no lags on the geometry part.