My wise and wonderful pitching coach of decades ago once told me that just about any pitch I threw could be turned into a nice changeup, and he demonstrated several such for me and showed me how to throw them.
My guess is that Steve Strasburg was throwing his changeup all wrong, and that was how he threw out his arm. Granted, some changeups are more difficult to throw because they put more strain on the arm, but why was he doing this? Doesn't he realize that there are changeups and changeups, and some are easier to throw and control.
For example, there's the palmball. This was the first changeup I acquired, at age 12---this is the one often referred to as the "Bugs Bunny" changeup---and it is one of the easiest to throw, because you throw it exactly like a fast ball, no ifs, ands, buts or bases on balls. The grip is simplicity itself; you grip it with all four fingers on top and the thumb underneath for support. The whole point is not to grip the ball too tightly, because you don't want to squeeze the juice out of it!---a firm grip, well back in the palm of the hand, hence the name. But you can change up on this one, either by loosening the grip a bit or holding it further forward in your hand. I had great success with this one.
I think Strasburg needs to take a good look at his grip, and he also needs to avoid changing his arm speed to slow down the pitch. 8)