Great breakdown.

I tried something simpler once, trying to map str.format() to a binary operator in Py3k.

http://github.com/jcsalterego/py3k-atsign

Needless to say it didn't pass the python-ideas (or was that python-dev?) mailing list trial, mostly because it produced ambiguities that plagued the % operator, which prompted this new str method in the first place.