There's no harm in releasing your own module, but I'd certainly welcome a patch to Perl6::Junction.

I was planning on using a startup-eval method to add the arithmetic operators, similar to yours but creating a 'real' subroutine rather than a sub-ref in a hash. What's holding me up though, is getting the time to write the tests, which as dragonchild suggested, is no small task.

(If you do wish to contribute, including tests would be good :)