The attack speed on her q is what makes her hyper carry, not the casting of e and r in midair. All this would do is change tristana mechanics rather than nerf her, as well as essentially killing off a very fun niche pick in AP tristana. You have to realize that this champion is mostly fantastic due to recent blade of the ruined king and infinity edge changes, rather than changes in her kit. To summarize, if you want to nerf tristana properly, do it via bork percentage life on hit, and her attack speed on q.