A little while ago Marc, I mused on whether you had thought about creating some more arid, desert style vegetation to complement your excellent temperate pack. Did you ever get a chance to look at this?
As I start to reach the closing stages of my current UK RW route, thoughts are turning to the next one being set in warmer climes - somewhere between Grand Junction and the California Coast. Nothing like a dull, overcast 3 deg C British winter to focus the mind elsewhere!
Anyhow while the default Cajon plants in RW are a start, no substitute for a quality third party pack.