Sorry that it's taken me so long to get back to this thread.
I see a lot of ideas here that I would not have thought of. Some of those ideas are not going to be feasible for what I have in mind. Some might work, but I'm taking it in a different direction. And some, I'm going to use.
For example, a small black Sharpie type marker would be a good idea. Low weight, marks rooms that you've cleared, and marks tourniquet times. Also could be a triage device, if you're medic trained (I'm not, officially.).
The crow bar is a great idea to have in the car. I'm shopping for the right one to get, but will in the end probably go the
old cheapie route. I should keep one in the car for getting into wrecked vehicles, anyhow. It's just too damned heavy to carry in a fast bag.
Extra magazines for distribution. If I could guarentee that the other officers were from my department, that would probably be a good idea. But in my little town, backup usually comes from a deputy or a cop from the town next door. No one knows what type of weapon or caliber that his backup will carry, except in long guns (everybody carries a 12 ga, almost everybody carries a .223 semi auto rifle.). My duty gun is (blech) a Glock .357 sig. The deputy who backed me on an open door the other night had a Springfield Operator .45 acp. Our BUGs didn't even match.
The question was asked about a loadbearing vest. It's a good option. I won't deny it. Jeff White (whom I respect the opinion of) likes to use them, with extra body armor. We do keep an extra tac vest in the car, and I could try to hang all of this stuff off of the tac vest. I have several reasons why I don't want to do that. First and foremost is laziness. I don't practice tactical techniques daily. Why? Well, I've got a life that demands that I attend to other things. So, while I shoot more than most cops, I'm not running around with tactical gear on, practicing assaults on buildings, much. Tac vests are worn on the body, and the gear is not immediately apparent to the wearer. In a light bag, one can simply take cover and LOOK into the bag. Also, a light response bag can be transferred to another. The bag can be left at a staging area. The bag can be supplemented to a vest. The bag doesn't interfere with the stuff on the belt. The bag doesn't hide one's badge of office. The bag is discreet, for when the "All Clear" comes down, and we stand down, exiting with cameras in our faces and soccer moms driving by. (The model that we use on Active Shooter training is for a school shooting. Let me tell you-- you park ONE cop car in front of a school, you get upset looks and calls from parents.
Two patrol units parked in front of a school will cause a whole-scale panic, with 911 lines tied up.) I also like the idea of having the oversized web belt along to sling up a downed person for evacuation. Let me tell you-- moving a 250 cop with a team of 4, while keeping yourself aware of your surroundings, is a chore. A sling around the chest would ease that a LOT.
I plan to try out the LBV option. Who knows? I may find it the best option.