Dangling straps and hoses. My BC came with 4 adjustment straps that, once properly adjusted, just dangle there. I'd attempt to reach a dump valve and inevitably I'd grab one of these. I've started modifying the strap D-rings so they hold close to the vest, and shortening extra long straps to fit me. I've spent hours practicing with different computer locations, retractors, clips, etc until I've found one that works. I've spent freaking WEEKS thinking about the best place to stow a safety whistle. (Still haven't decided.)
So you adjusted the straps to fit YOU. Once they were just right, you took care of the excess material.
You want an agency, a book, or a something that will dictate how to do what you did? Didn't you have a blast getting it JUST right?
After WEEKS considering the placing of a whistle, do you really think anyone will know better than you where is the best place? pick a place that appears the most logical one and reassess after a few dives.
My first set of gear was a bunch of cheap and old parts and pieces, but every single item was adjusted to be just right for me, I didn't leave anything untouched, removed stuff in one area, added on other. During no less than couple of hundred dives I made a point to consider all those adjustments: keep as is, adjust more, remove all together. After every thing was anally perfect some bastards broke in my house and robed pretty much everything that wasn't nailed down.
Since then I've gone through several sets of gear, much better quality stuff but still today I miss all the concoctions I put together back then. I had a great time doing it and I can't described how much I learned, not only about the mechanics of the gear itself but more importantly that a good diver can enjoy a dive with very little.
If you know what you are doing it doesn't matter if the air comes to you from a steel bottle, aluminum, a hose from topside, or from a goat bladder; you'll be able to adapt to the circumstances and have an enjoyable time.
I think most important is to be used to your gear and have everything always on the same places.
For me that was the most important thing when I started: once a place is decided for an item, that item goes there ALL the time. Another important factor for me was to follow the same order. The gear bag was filled in the same order also, starting at the toes with fins, going up the body with the rest, all the way up to the head with the mask and hood. For gearing up I also did it the same all the time.
Now I'm old and jaded, all my stuff is in the boat all the time, my anal pursue of perfection has diminish a lot.
to take this a step further... wouldn't it be easy if everyone had their gear rigged in a standardized way? That way you know exactly where everything is on everyone you dive with?
I imagine there are good reasons for that type of uniformity, but if I ever were to pray for something, it will be for that to never happen.
Divers are a bunch of different types of people. For you a whistle may belong on the left upper side of your gear but I may like mine by the inside of the right ankle.
Just my opinion obviously, but there are enough rules in diving, no need to add more.