If you have items that always live in your pack, haven't you already placed them in a container?

Or maybe I'm not entirely sure what you mean when you say "containerize". Do you mean putting certain items in certain location, possibly in a container for the purposes of organization, as redundant gear or specialized emergency equipment? I put my back up gear in a container, that I can move from pack to pack, and I just leave it loaded at all times. A single item to grab is faster and easier than double checking against a checklist.