It would be a nice thing to try if you have found a particularly good looking rhodo trunk, but other than that...?
This would be the main point for me, some available good trunks. I was thinking that the thread graft would be easier due to the thin bark and difficulty lining up the cambium layers.
As far as the size issue well, I guess it's an impatience thing, my growing season is definately shorter than Cal's, and rhody's get much bigger here than azaleas much quicker.
Guess this will be my chance at pioneering.