Great idea Kirk,
Julie Firth in Geraldton, Western Australia recommends this approach too. She has found that using, for example, Acacia aneura, a nitrogen fixer of desert provenance has shown much greater success in the slightly less that desert-like Geraldton. I think that this approach will become increasingly important in the face of climate change.
I hope to keep up with your project. Will you be documenting it on your blog? I've subscribed to it now in any case.
I'd like to be able to use mesquite here in WA (Western Australia, not Washington

but it has a tendency to rampancy here and is outlawed.
May your polyculture be overyielding,
Harry