I will have a look on all this idea ... to my part i think that the best it s to play with the physic engine. In m project, we use Physx from Ageia and in some tutorials we have see that we can use this one to do the stuff.
i woukd like to know how could i modelise a 3d scene that i could break, with for example a Gun.
By the way, i don't search a physic engine or other, but just the way for how represent into a 3d level tool. ( i m currently use GTKRadiant for having a pk3 at the final).