Go for it, Dylan!
The sidearm delivery is the most natural and the easiest on the arm and shoulder---I should know, because in my playing days many moons ago I was a true, natural, dyed-in-the-wool sidearmer with a consistent release point. I wasn't particularly fast, but I could throw hard, I used a slide-step (which added some speed to my delivery), and I picked up and made very good use of the crossfire. You say your pitching coach is all in favor of this transition, so go for it. You may gain some velocity; what you definitely will gain is more control and command of your pitches, and if you can add the crossfire to your arsenal you will be just about unhittable! Not to mention less arm trouble, if any. So I say, welcome aboard to this specialized aspect of the bump.
