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Just another couple of thoughts for you. You do have other options, but here's why I still recommend the shoulder bag.
I have the Think Tank modular belt system as well. To use it with two bodies, you need to have straps to hang the bodies over your shoulder, or attach to the harness system Think Tank makes. That's okay in certain circumstances, but you will look pretty much like a soldier in full combat gear or a walking camera shop with the gear you say you'd like to have access to. I use this setup (with fewer pieces of gear), when I want to be highly mobile, flexible, and not having to set my bag down to switch up or get a quick shot (e.g. shooting a rodeo). I shoot football also, but have found that two bodies with a different lens on each is what I need for that, so no bag or belt system is required.
Backpacks are also an option, but to get to anything, you have to take the bag off, lay it down, and get what you need, put back what you had, and either put it back on your back or leave it sitting on the floor/ground. For me, photo backpacks are for hauling, not for shooting. (I have several, so I'm not knocking them.)
Rolling cases are also an option, but again, you need to put them down, open them up, get what you need, and move on. As with backpacks, they're best for getting your gear to where you need it, but not really good for changing and shooting on the fly. For that style, I still think a good shoulder bag is the way to go.