For approximately the same needs (accessibility and speed anyway), we're very reliant upon the Tamrac belt pouches. I'm not a fan of their belt, but the pouches attach nicely to the waist belt and shoulder straps of a pack. And a matter of fact they attach well to almost anything else when you're not using the pack. Since trying them out, I can't tell you when I last used a photo vest. As for the solo carry of a body with a mounted lens, I'm not satisfied with any product I've tried.
One large help was to get rid of the infernal short camera straps in vogue today and replace them with long versions so I could slip my head and one arm through the strap and dangle the camera down at waist level. It carries more comfortably while being out of the way. You can rotate it around so the camera rides on your back rather than the front too. That's ideal for active use in most situations, but won't work while wearing a backpack. Even so, it's awfully nice to get that camera down low and under your arm where a squeeze of the elbow secures it from swinging while you're doing something else.