The demons of the Abyss are all about chaos and random violence. They're not devils. They don't have a strict hierarchy.
So what about a version of the multiverse where the demon lords really aren't much more powerful than other powerful demons? Maybe Demogorgon, Orcus, Graz'zt, et al. haven't been lords and princes for millennia, but they just happen to be the ones who are in control at the moment? There's a part of me that finds a great deal of appeal in the notion that the ranks of the demon lords shift on a semi-regular basis, maybe even as frequently as several times a century. I think, if played properly, it could actually add to the chaotic feel of the Abyss, and further differentiate the demons from their lawful Hellish counterparts, who do have a strict hierarchy that has lasted (more or less) for thousands of years. It would also lead to a lot of conflicts between demonic cults, as the Abyssal struggles for ascension are mirrored in their mortal servants.
Again, not in-line with planar material as written, but I think it could make for a really interesting variant.