TorBlock is a bit to specific in what it does for how generic half the code is. Part of what TorBlock does is the actual identification of Tor exit nodes, however that's not something specific to TorBlock. There are a lot of other uses like CheckUser identification, extensions to note Tor usage in places in the UI, or even alternative things like ConfirmEdit could require captcha from an anon Tor user rather than flat blocking anon Tor users depending on local policy.
But basically what I'm saying is, just like how we have SimpleRegex which is used by two or more of the Regex based extensions, It would be nice if half of TorBlock was cut out into a SimpleTor extension which would handle the basic parts of identifying Tor nodes. Then we could make features in other extensions depend on SimpleTor and use it's shared functionality to build those checks in.