I'm thinking along similar lines, but my approach is to eliminate refcounting entirely. (Note that the incref and decref macros could still exist for backwards compatibility, but would do nothing.)
There was a PyPy talk at this year's EuroPython about "writing code for different GCs". Certainly worth reading in this context. Bottom-line being that it's always worth thinking about the effect of ref-counting on code and if the code would still work if there was no ref-counting (as in Jython, PyPy and IronPython). Sometimes not as obvious as it might seem...