Right on, ish! Long ago, my incredible pitching coach told me that just about any pitch can be turned into a nice changeup, and he demonstrated a few such for me. So when you have, oh say five different pitches, and you can throw them at two or three different speeds, you have almost a closetful of pitches to choose from. The important thing, of course, is control and command.
I don’t know what arm angle(s) he uses, but I can tell you, I was one of those infuriating sidearmers, and as such I had an extra advantage no other type of pitcher has: the crossfire. This is a beautiful and absolutely lethal move that works only with the sidearm delivery, and I fell so in love with it that I used it most of the time—a fact which was not lost on my pitching coach. One day he was helping me resolve a problem I had been having with my circle change, and he said to me “I know you’re going to crossfire it. You use that move with everything you throw.” That move gave me double the number of pitches I already had! 8)