A combination of sinking units partially into green terrain, like ARMA2 does, combined with a shader to fuzz the edges of objects next to the terrain. Add another shader to make the rest of the terrain noisier. It's a very rough approximation, but shouldn't be too expensive.

Ezcoo, if it's possible for many games to switch to desktop and back instantly (a somewhat harder problem), I'm pretty sure it's possible to make the transition between game and a 2D map instant.

In fact, I know it is. Not only do plenty of games do transitions between 3D view and map instantly, I've written code that does it myself (a basic way is to create a polygon that covers the viewport, use the 2D image as the polygon's texture, and maybe change the projection matrix). ARMA 3's current transition delay is a shortcoming of the current implementation, not something intrinsic to how 3D cards work; I'm willing to bet it's an artifact of BI's internal developer organization. It also happens to be a rather annoying shortcoming, because it makes using the map a chore. Fortunately, this is alpha.

Coincidentally, that loading screen is 2D as well, yet there is no blank delay from it to the gameworld.

I was very surprised to have the control tower fall apart around me while testing grenades. Two grenades do indeed do the trick.

I should be able to thrown grenades all day in a concrete building. It'll destroy all the windows and doors, but the structure itself shouldn't fall apart.

I imagine that ragdolling corpses will also be a problem in multiplayer.

One thing I've not been clear on is how BIS would handle ragdoll in multiplayer -- if bodies are falling in different positions on different clients, it means different players have different lines of sight and (some modicum) of cover from a body. Tossing bodies into new positions just complicates it further.

If a client transmits the final position of a fresh body, and all clients thereupon treat it as a static object, that would simplify things a lot.