I should point out that you're talking about different functionality, destructibility and scripting. On Red Faction we had full scripting support to set up the scenario you describe, but found that it was much more fun to give the player an excuse to level a structure entirely. It's really just a philosophical distinction…
What Will said :) Modeling the system you described is not difficult, it just doesn't provide anything meaningful to RFG/RFA's gameplay. The whole stress/fracture system that GeoMod 2.0 used is rather complex, and you'd do yourself a favor checking out the GDC presentations. AFAIK Battlefield's destruction (at least in bad…