Here is a v1 patch series that does the first part of what we've been talking about, which is to implement the new optimization rule for the case of a single RHS reference to the target variable. I'm curious to know if it helps you at all by itself. You'll definitely also need commit 534d0ea6c, so probably applying these on our git master branch would be the place to start.
I'll apply these tonight and get back to you asap. There are many functions in my API that take only one expanded RHS argument, so I'll look for some cases where your changes reduce expansions when I run my tests.
