I really like your idea of using modules. For me, the only argument I have in my case is my two primary kits are designed for two very different situations. By having duplicate modules I increase my chances of having one of the two kits with me. However, the big survival kit includes exactly what the small kit does plus a few other modules. This ends up up with having a kit of appropiate size for situations around town or light day hikes and another kit suitable for more intense situations. As to the rest of my gear I have switched to thinking in terms of modules.

I must say your everyday situations are probably less intense as the situations I could see myself in based on the amount of gear you carry. I think in terms I am preparing for a true survival situation and under those conditions what would I truly need to survive.

In my case your small kits although very comfortable to wear would leave me shorthanded in many areas.