This is a solid design. I personally don't like that it's strictly better than mocking sprite. It's not unprecedented though!
I have an idea that makes it slightly more interesting to me, and not-strictly-better than your inspo. What if the mana cost was {1}{U}{R/W}? Or even {1}{U/R}{U/W}? This plays with the colors of those two abilities- spellslinger is primary in UR, and flying is primary in WU. So this creature could feasibly be mono-U, UR, WU, or even RW!