Hey all I'm back from the dead!

Anyways I ran a search and couldn't find an answer to this so forgive me if it has been answered many times. I asked this question a year and a half ago, but I don't remember the answer.

I'm making a tactical first person game. My levels are going to have nonlinear indoor and outdoor levels, or most likely outdoor levels with buildings to penetrate. I plan on having highly destructible levels, example the player most penetrate a base structure, but he isn't told how, he may want to blow a hole on the outside of the base. Stuff like that. Also indestructible cover sucks in my opinion.

I know basic advantages of blocks and models, but I've never really got into level design and I haven't touched 3DGS in over a year (life happens).

Any help at all in my understanding would be great!