@Zef
2. the key to that is to use a piece of fabric chalk the tailors use. Strike through all of the d-rings, and the points where the webbing crosses over on the harness. When you take the first piece of webbing out, lay it against the new one and transpose the chalk marks over. It will be set up how the first one is. If you decide to go back, the first piece still has the chalk on it to make putting everything back easier.
4. the crotch strap one helps quite a bit with suit abrasion, but agreed on the shoulders
6. I still botch that one and curse myself when I have to undo the left side because I hate threading belt buckles
8. BINGO!!! been saying that for years. With the big ss plates, you shouldn't need more than 2 weights and it's easier to deal with a belt than pockets
9. jynx since I was going through this in order
11. most of them are pretty close to the same thickness, but the delta is usually less than a pound. They're all pretty much 4.5-5.5lbs unless you have a short or a long one. Couple exceptions, but they're all pretty close. Which ones did you see that were different enough to note?
12. if that's a major problem for you, you may well qualify for a transplate. The problem with going sidemount is you have to rely on a cart of some variety to wheel stuff down and that isn't always practical. The transplate is designed to transfer the load to the hips like a hiking pack and you may well be a candidate for that. John has Red and Blue in a bunch of sizes, though the sizes are basically just the length of the shoulder pads. I would urge you to get one of those and some sort of back pad for the backplate to shift all the weight down to your hips and off of your shoulders. A proper fitting one-piece harness can start to do that, but isn't nearly as comfortable. With upper back problems, the $80 for one of those is probably a worthwhile gamble
Large - Dive Rite Transplate Harness - Red -Large
the "doctrine of standardization" you talked about is really a small group of the tech community. The rest of us that end up diving with most of the stuff in the same place is just because it also happens to make the most sense. I deviate on several things and most all of my buddies do as well, but the base configuration is that good. We don't care what is in what pocket where, we don't all have the same primary canister cord routing, some of us don't have steak knifes on our left side waist strap, etc. That said, the sidemount and CCR side of tech diving have botched just about everything in standardization since they are all so personal.