Continuation of the D&D brand (from a business perspective)

[Hoddypeak]

Also, two sets? I'm thinking variable subsystems that can all interact with each other. Pick one of two in column A, pick one of five in column B, pick one of three in column C, so on and so forth.

I'm not locked in to two sets of rules. You could certainly have more. For instance, in terms of combat rules, I can see three or more sets being reasonable. A quick method that draws on OD&D or AD&D, a more detailed miniatures based set that follows the 3.X or 4e style, and a set for large-scale mass combat. I'm sure other people can think up more ways they'd like to see it go too. But the more sets you have, and the more detailed the rules are in each set, the more room there is for broken combinations to unexpectedly show up.

If I were in charge of designing an edition and went this way, I think I'd lay out the possibilities for these types of things, and then narrow it down to two or three options in a few places to start with, knowing that over time, as 5e runs its 8+ years, more sets can be added in. Then I'd put all the simple versions together into a PHB or a boxed set and call that Basic D&D. That would be the simple combat rules, the simple skill system and no-skill system options, and the kindest magic system. Then, I'd sell books with an AD&D title for the other sets, as they'd be more complex and rules heavy, and thus "Advanced."