I've heard about any fruit tree wood is suitable for pipe making. We have olive wood, pear wood, cherry wood, and others already so it seems to me that there'd be no harm in experimenting. Besides if you've already seen lemon tree wood used I can't see why orange couldn't be. If you can get some I'd encourage you to experiment. It's probably already been done anyway by somebody somewhere out there at sometime and at least we'd all be able to hear whether or not it makes a decent pipe straight from the horse's mouth if you do it.
Do it for the good of us all! For the science of pipe smokery!