A step-up from TiddlyWiki that is still 100% portable?

TiddlyWiki is a great idea, brilliantly implemented. I'm using it as a portable personal "knowledge manager," and these are the prize virtues:

1. It travels on my USB flash memory stick and runs on any computer, regardless of operating system
2. No software installation is needed on the computer (TiddlyWiki merely uses the Internet browser)
3. No Internet connection is needed
4. In terms of data retrieval functionality, it mimics a relational database (use of tags and internal links)
5. Set up and configuration are so simple as to be almost zero. This would also mean dependencies are so minimal as to be transparent, or nearly so.

Let's say I've got a million words of prose in 4,000 tiddlers (posts). I'm still testing, but it looks like TiddlyWiki gets very slow.

Is there an app like TiddlyWiki that keeps all the virtues I listed above, and allows more storage? (or rather, retrieval!)

NOTE: Separation of content and presentation would be ideal. It's nifty that TiddlyWiki has everything in a single HTML document, but it's unhelpful in many ways. I don't care if a directory of assorted docs is needed (SQLite, XML?), as long as it's functionally self-contained.

After some time and serious consideration, I will post my own answer.
There is nothing that matches TiddlyWiki.

As for voluminous information, TW can pretty much handle it. (My early discouragements were due to malformed code.) Difficulty accessing information through the interface becomes an issue before any speed problems. This isn't to fault the interface -- it could be more powerful, but that would sacrifice lightness.