I'm not an avid hiker, but am a gear junkie. I have several different packs for various purposes and hobbies. I am gearing up for a hiking trip to GNP this July. I was re-examining my pack and some things I plan to carry. What I've found is that backpacker packs are pretty straightforward – you buy a design for the components it has. I realize many here want light weight and mass volume. I understand that, but when you want to add extra stuff, how do you do it?
I have a tactical backpack, with molle attachments. I can add extra space when I need to. I can attach first aid kits outside my pack, so I don't take up my cargo space. I can add additional packs on the exterior for quick easy access to common need items. What's more, it makes smaller packs expandable for times I may go longer and need more. Right now, I'm simply trying to figure out how I want to carry my bear spray. I have a molle attachable case that will hold the bottle, but no way to attach that anywhere on my kit – shoulder straps or waist band. It won't do any good in my pack when momma bear is galloping towards me.
What modular back packs are out there for a 40-60 L pack? Why haven't the major brand developers adopted the molle concept? Seems to me there is a design opportunity.

