Please bear with me. I'm going to suggest something from far, left field. This may sound crazy, but I'm one of those outside the box thinkers.
How about a mesh, fishing vest? Now hear me out, before you totally discount it. It's light, breaths well, holds a ton of stuff, everything is within easy reach, organized, keeps everything dry when deep wading, and it's relatively comfortable. It doesn't limit vision and get in the way with casting, like a chest pack. It keeps things out of the water, unlike a lumbar pack. The downside is, you'll be the only fly fisher, other than me, that uses a vest.
I have all three. 3-4 vests, 2 fanny packs(fishing specific), and a couple chest packs. I used the chest pack last weekend, and it reminded me why I don't like em'. For minimalist, I like a fishing shirt with bellow pockets. For everything else, I like a light, mesh vest. Currently using a 3 year old Simms I bought on closeout. I carry a LOT of stuff. After time, I know what is in what pocket, and it takes 0 effort to find anything I need.
.....yeah, it's probably a stupid idea.
briansII