The design process of this card was pretty straight-forward, honestly. I was looking through the cards in my peasant cube to find room for the new [[Mocking Sprite]], when I glanced at the always-reliable [[Warden of Evos Isle]] and thought “Wouldn’t it be cool if I could get the effects of both this cards in just one?”
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!
Agreed, the inspiration cards are already plenty good for the cost. If you didn’t want to go into another color you could cost this at 3U or maybe 1UU.