Ah I see where you're going. Like the wordpress ecosystem. There are people who actually make "wordpress" the app itself (the metaphor for chain here), then there are people who make plugins (the metaphor for dapps here), or the people who make templates (your metaphor for skins here) and so on.
Or those who make or suggest things for things like games, where people make artwork, music, marketing materials, explainer posts, additional user generated content, like say maps or puzzles for a game that allows them to "mod" it or add to a DLC catalog for it.
To some degree nothing is stopping any of this from happening already, but there are no official guardrails on most of it. If any are even warranted?
Interesting stuff to consider.