For options that can be "nested" inside another options, I think it makes sense to write the basic framework once, and then swap out components of that option family.
I can imagine nesting the classic hit point system inside a lightly detailed lingering wound system inside a very detailed lingering wound system. This is a dial for a wp/vp point system which would be equivalent to pure hp at its lowest level of complexity.
The reason for doing something like this is more than just preventing some redundancy in the optional rules themselves, it also means any game elements that deal with wounds elsewhere in D&D work the same way for all of them, and that the DM can temporarily elevate the dial in special cases without introducing rule contradictions. For example, suppose vampire bites cause wounds on a critical hit. I don't want to write a version of the vampire without the wound, plus different wounds for the different levels of complexity. Rather, it is much better to write it once and work with all the dials.
Suppose I'm fighting vampires with the lowest (hp only) dial. Most wounds are simply ignored (the null wound), but maybe the DM loves the flavor of the vampire's critical wound and temporarily elevates the dial just for that kind of wound. The game continues perfectly well and without corner cases because the hp-only setting knows about wounds, it's just that the only wounds that normally appear can be transparently ignored. In this case, however, the wound really occurs. Now suppose the cleric's "cure light wounds" ability either removes a minor wound *or* gives the user 15 hit points. Normally the cleric in this game only ever grants hit points, because all wounds are null wound and can be ignored. Nevertheless, the spell was written to be aware of wounds so it would work with all settings on the complexity dial. In this rare case (at least for this particular campaign) the cleric can use it to remove the effect of the vampire's bite.
Or maybe the game uses the highly detailed wound system, where the wound location is rolled randomly and causes additional effects based on this. But in our vampire battle perhaps the DM just decides the wound goes to the victim's neck, period. Either way, this setting of the dial doesn't require rewriting the vampire's stat block because the complexity dial modifies the base wound in a perfectly enclosed way.
I think this is an elegant way to make modularity operate smoothly. First define a default, what "most" people will use. Then define a lighter version of it, but one which has a "dim awareness" of the part it functionally ignores. Then define a heavier version which modifies the normal method in some more-or-less self-enclosed fashion. Then write the rest of the game assuming the default.
