That’s right. If you import a bundle.json file into a wiki it is converted from the “Array of tiddlers” into a plugin-like $:/Import tiddler, as you pointed out.
So clearly the core contains the functionality to convert from and to those structures. But full control over these functions is only available for plugin authors, at the moment. ATM The documentation is “read the code”, which makes it a bit hard to learn 
That’s one usecase I also wanted to explore for quite some time. … Since TW UI can be 100% controlled with state-tiddlers, it’s possible to re-store different “UI states” by manipulating several state tiddlers at the same time. … OR as you wrote: “Restore a known state”.
But I do want to go much further. … Inception like … Like a bundle, that contains a plugin-like tiddler that contains a series of plugin-like tiddlers.
More brainstorming details to come in a different thread, so I don’t want to derail this one.