Make the corporations more distinct I would sugguest that working for that corporation should give you a boost with the weapons they supply so its advantageous for your corp to dominate, so you get their weapons and an advantage. Make it other things not just headcrabs , zombies etc. get mercs (combine npc) to protect spawns of corporations. Make them killable but they respawn after 1 min so they are a deterent againts camping the npc`s but not imposible