The thread title is a typo of sorts. I am actually interested in desert as a final result.
I figured that while grasslands to desert in one step would be ideal, a short step to plains is also acceptable because, as you said, scorch completes the transmogrification needed.
You've also covered pretty much all the other thoughts I had on the matter. I was hoping there was some arcane ability that might not be very well known that would do the trick.
Hell, with the fuzzy line of demarcation between documentation of what might be in FfH2 and what actually is a feature, I figured I'd be in with a good chance.
As a by the by: my housemate wants to turn a one tile wide and two tiles long choke point into a killing zone via desert's movement and defense penalties.