Ah, interesting. Well, the current template feature can do this halfway right now, maybe… If your Template A looks like…
Some text
- [[Template B yyyyMMddhhss]]
- [[Template C yyyyMMddhhss]]
…where yyyyMMddhhss are timestamps using the Template’s syntaxes, those two notes would be created as orphans. They could then be manually filled with more templated content.
But yes, I get what you’re going for. Nested templates, essentially. A good candidate for a plugin, I imagine.
Alternatively, you could probably use automation/macro tools to create these nested templates using e.g., Keyboard Maestro (macOS) or AutoHotKey (Windows).