Nice idea. … But there are some pitfalls. Nothing within a plugin tiddler is visible out of the box.
Have a look at my post HowTo Compare the Content of a Shadow Tiddler With the Content of an Overwritten Shadow and you’ll see that it’s relatively complex to access content within a plugin-tiddler.
That’s by design. Plugins are only needed at startup to create shadow Tiddlers. So you don’t get any optimizations like: search, backlinks, tags, filters or internal caches and indexes, that can speed up tiddler handling.
So imo that’s not really an option for that special usecase.