Glad to see some attention on the real topic.
I decided to take a look back at Killzone, and I can't help but notice how much system power it takes to run the AI considering you can change the number of bots on yours or the opposite side in the multiplayer mode if you choose to run bots that is. I tried running the MP with Me + 7 bots against 7 bots and the system was struggling, with framerate picking up gradually as you lessen the number of bots. I remember during the time leading up to its release the Official Playstation Magazine did a feature with Guerilla on the game, where they tried it out, and they did talk about the AI, of which they specially built with self preservation. Idk how much of that "AI they had initially created" got displayed in the real game, but there is no doubt it's using some serious processing muscle it seems out of the EE in the final product. Killzone I think makes an interesting case study, considering it rode the hype machine until it's release to only IMO ultimately not exceed expectations though it's still a very interesting IP that has serious potential. It just should've been on the PC like originally intended. But more on topic, in regards to Killzone's AI I think that might be why there isn't much more to the playable field in this game like physics enables entities like barrels, crates, etc, or even a real ragdoll physics system: too much system burdening. Some other games that were kind of noteworthy to me I think were Area 51 with it's ragdoll as well as some physicallized objects, same with Psi-Ops, as well as Cold Winter which had the full ragdoll, not to mention real gibbing (yes you could shoot off limbs and they still were physics influenced) and pretty much every barrel, table (you could throw em over for cover), or "loose object" in the game had physics to it which I found rather surprising and impressive on a PS2 game and it I think also is an interesting case study.