I use the Ribz in summertime around town for my EDC-stuff when it is too warm for anything else than t-shirt and shorts.

Back in the 1980s and early 90s I (and many others) wore a Domke photo vest. Many pockets. It did not wear all that well with a backpack though.

Many survival situations are caused by injuries of one sort or another. Therefore first aid is important. Most FA rigs can be improvised, provided one has the knowledge, it would be worthwhile to carry at least one 4x4 sterile dressing, and maybe even a 4" elastic bandage...

Realistically, the contents of a minimum survival kit will vary with the season and the environment.

After injury (or maybe before) many survival situations are caused by people simply getting lost — “Doh! Where am I”. Wandering off and then suddenly realizing they don’t have a clue how to get back. So should a minimal kit also include a GPS or Map & Compass? Probably, but would basic navigation meet your minimal criteria test. Once you start including all the just-in-case contingency items, you don’t have anything close to a “Smallest possible survival kit”.

Do a Google,DuckDuckGo or Dogpile search for “10 Essentials” and see what’s left when you remove everything that’s unnecessary. If you’re honest, you’ll probably find at least 10 items.

I can get a fairly useful kit onto a wallet sized space: folding knife, lighter, cordage, cash, ID, pen, safety pins, needle and fishhooks in case, tape.

the cordage in this case is 20-50# fishing line. Usually 3-10 meters.

An altoids sized kit - though I now prefer a waterproofed plastic one.
room for cask, a small knife, fire, tape, fishing line, safety pins, etc

Although a wallet with cash & cards and a phone with useful apps will likely get you faster, farther and warmer...

The Hill People Gear Kit Bag is a great pack to carry a minimal kit. It's primarily marketed as a way to carry a handgun so when I see one I automatically think "gun"...but other folks use them differently. It's a chest rig, and there are several models from smaller up to fairly large. My buddy gave one to his dad who has Parkinsons, he uses it to keep his meds and stuff he needs to keep on him.

Even with a sidearm you could still easily fit a light, knife, pair of space blankets, cordage, BIC lighter, a bit of tinder, a compass, etc. When overloaded it's not super comfortable but up about five pounds it's not bad at all.

It does look pretty tactical but they make one for SAR that looks much "sportier".

I'm playing with a wallet to cell phone box sized kit right now. I like a tupperware that fits in a pocket.