Gahhhhh, this is a superb idea, but the thought of implementation for one such idea would be a colossal mess... The engine is flexible, and with the introduction of these new features in ArmA III would help, but some of these ideas are very hard to achieve even in A3... Most scripting in ArmA 2 is in game code, and doesnt have much effect on what the program sends to the GPU, what the OP is trying to achieve with say breaching or the ability to destroy elevators would look awful in a game engine such as ArmA, whenever scripts in ArmA do move something and change what is being rendered in ArmA, it is clunky and often an eye saw... eg. disabling land mines, blowing up buildings etc. hopefully a better ragdoll and physics engine can fix the graphical side, but there are still huge problems on the script side, scripts that change something graphically are often heavy and they have to instruct exactly what the object is doing etc.
As for the rendering in ArmA 3, ask yourself, is it really the engine to be using if you want an insanely high poly count (the city) to run smoothly? I can guarantee that it will not run smoothly unless you render the outsides of buildings and then allow the players to enter them and ditch the outside assets to load separate inside assets, which is not supported by ArmA either.
ArmA's engine runs incredibly glitchy mechanics when it comes to objects being able to interact with each other, for example, you slam a car into a building, the car then get stuck, or while inside, your character falls through the floor and gets stuck... and back to scripts and animations, they are just a technical nightmare waiting to happen in a CQB environment taking place inside an object, not to mention a gameplay nightmare...
I really like this idea, but it would need to take place on another engine eg. something that supports volumetric objects and standard poly objects.
We'll see what this engine can do though before I say its impossible.