A pistol belt w/ suspenders and the rest was the system I used for the longest time. On the belt, I carried two mag pouches in the front and one on the left side. One was a FAK, the other was everyday items like note a pad, etc. and the third had emergency/survival items. My fixed-blade knife was on the right. Two canteens, one over each hip pocket. One canteen cup. Compass pouch on one shoulder strap and an angle-head flashlight on the other. The butt pack contained a poncho, extra socks, food and anything else bulky.

The beauty of it was that you could get at anything except the butt pack on the move and without taking it off. And then, your buddy could get something from the butt pack for you. During GSAR (Ground Search & Rescue) training, we literally lived in our gear for a solid week. It didn't catch on low-hanging branches, get jammed between two close-set trees or knock over the guy standing next to you if you turn suddenly like a framed pack does.

Once I somehow ended up at a Boy Scout event where we had a certain packing list of gear to carry and we went around to different stations where we had to make a fire and boil water, tie a knot, etc. Every time we needed an item, I would have it out before everyone else's packs hit the ground. By the way, I never got the packing list, I was just carrying my normal load-out.

But as Tom_L said, ammo pouches are designed for storing ammo, not first aid kits.