I'm -1 on your second case.  That syntax is too magical, especially since a test method can appear on more than one test case.  

The additional pattern matching suggestion is more interesting, but it would be necessary to implement that in unittest, since test classes and methods can be created on the fly. I suggest opening a new issue against unittest to extend pattern matching to test case and test method names if you think that feature is valuable enough to add.

I agree with Sandro, I think the valid part of this request is satisfied by the unittest CLI.  It is true that more work needs to be done before all Python tests can be run successfully in this fashion, since some depend on regrtest features.  But making those fixes (moving useful regrtest features to unittest and eliminating the non-useful regrtest dependencies) is a better investment of resources than adding run-single-test support directly to regrtest, IMO.

If you want to submit a patch for first case, though, feel free to reopen this.  I doubt we'd reject it if you want to do the work.