I think that understanding the reasoning behind the system allows you to make certain judgments of what you can or cannot borrow. If you don't, then it is possible to get yourself into trouble. For example, if you use a long hose with a snorkel, it is possible to accidently dislodge your mask during an air-share. When you go to donate air, your long hose will catch on your snorkel. At least, you dislodge your mask. As most, your mask pops off and heads 200ft down. Believe me, a no-mask ascent is tougher that it looks.
Let's say that you use a long hose with a BCD - probably a more common hybrid because it's the cheapest change to a BCD setup. Again, you have to ask yourself what could get snagged. If you have a BCD, then you probably have a console for your SPG, dive computer, etc. You may have dive lights that are clipped into the BCD. Where do you tuck in the long hose to keep it out of the way?
When I crossed over from a BCD to a bp/wing, it was a multi-step process. The first evolution was diving a long hose, bungied 2nd with a BCD (and my Air2). The next evolution was adding the bp/wing/harness. I wasn't comfortable with getting in and out of the harness, but I loved the way I was able to move through the water. As I gained more experience and comfort with my diving, I paired down the lights, the clips, the extra LDS toys to what I have now - a hogathian rig. I use the same rig whether I go diving in the Bahamas, wreck diving in the Great Lakes, or looking for critters in Puget Sound.