Its interesting to see sidemount take off after I was nearly crucified for advocating independent doubles a few years ago. I gave up backmounted doubles for the orthopedic reasons mentioned. I plan to give sidemount a go when the configuration becomes more standardized.
Not likely to happen. Like they say, put 10 side mount divers side by side and you'll see 11 different configurations.
I teach a side mount course and don't require standardization from my students. In fact, I tell them about all the different possible ways to configure things that I know of and leave it up to them to decide which way to choose.