Ranger,
I have been enjoying this SP, and just wanted to add a few points in regards to reality and IEDs.
Using tires is good, but not in the middle of the road. They call em road side bombs for a reason :). The blue barrels are good too, and quite common in the middle east. Another idea is using dead animals, such as dogs or cattle.
Spotting an IED in the real world is difficult at best. Not sure how to do this in the game, other than putting something like an arty shell in the tire and have it visible if you use your binos.
You put the IEDs at choke points, which is good. One option is to have an ied activated after you roll past it. Not set off, just set up. This simulates the bad habit of using the same route twice on a mission.
The guys who normally set off the IEDs are not armed so they can blend in after they set it off. One option is to have them laying in the prone watching, or another one with a video camera filming you. These are what we call threat indicators that add up to tell you something is up.
I know that the IEDs are just a small part of your mission, but I hope my observations may help.
My only other problems are game and ACE related, not mission related. The Bad Guys are way too observant and too good at shooting at times. My team needs to spend more time at the range since they waste a lot of ammo too :).