They make TONS of MOLLE accessories, you can basically customize your pack to carry what you want where you want it on them. It's a great idea! I have two MOLLE packs but I hardly use the webbing on them. I plan to though
You can put anywhere from flashlight holders to triple AR15 mag holders on them, canteen carriers, Med Kits, thus saving room on the inside of your pack for other goods.
If you do put a med kit on the outside, just wrap the contents in plastic as best as possible to keep moisture out!