Qalisto
Using the import facility you can import many file types into tiddlywiki. Text in particular will exist within the body or text field of the each tiddler.
Unlike the default import if you look at the BrowseWidget you have a parameter "multiple", where by it is easy to select multiple files to import at once.
Once you have all (or a sample of) your text files imported you can set about designing ways to manipulate the content of your tiddlers,
perhaps generate new ones with structured data, perhaps parse them or build a viewtemplate that interrogates the text field.
Perhaps you could extract information from tiddlers and feed it into data tiddlers or push it into the fields of tiddlers.
The sky is the limit if you ask me.
Regards
Tony