OMG you mentioned competition 👿
lol 😛 anyway, I am familiar with the Divi theme and do find it too complex for most users. I know they tried to get the theme to be like theme forest themes (which all look the same). There is always a problem with adding too much to a theme when being developed because the more you put in, the more chances something will go wrong. Updating these themes are an absolute nightmare too. The background sections relates more to a parallax theme which does have limitations, but can be done in other ways (that I am looking into).
With that being said, and your hints of functionality, not to worry because I will be doing similar features where you can have 100% width based sections, as well a fixed main menu as one scrolls. It will depend on the theme I create though of course. What you are hinting at is being planned for my next theme that I will be starting in October…as soon as I complete this next one later this month.