Bootstrapping Is Harder Than It Looks:
In my copious free time not taken up by a dozen other projects, I've been working on Module::Build::TestReporter to make version 1.0 available before Perl Testing: A Developer's Notebook comes out. (I still have yet to bundle Test::Kwalitee.)
After the first release, Stig Brautaset pointed out that there's a bootstrapping problem for people who want to use MBTR. It depends on a few non-core modules, but if you're using Module::Build::TestReporter for your distribution, it won't load without those dependencies -- and you want to mark the build dependencies in your Build.PL file. (You also need to ship MBTR with your distribution, but I can't do much besides document that fact.)
The approach I chose was to attempt to load the necessary modules, trapping any errors. If something failed, I install a different constructor that adds the necessary files to the build_requires parameter and calls Module::Build::new(), which handles the dependencies appropriately.
Testing that logic was a bit of fun, too. Sometimes I wonder if we test module writers test our test modules just to make us less smug.