Hey, the Assassin would really benefit from letting her charge-attack in mid-air. You could get easier to certain places and it would be easier to avoid getting ringed-out. /Discuss
She can't lunge because she's in mid-air. The Assault and Tank can charge in mid-air because they have jetpacks. The Assassin just leaps with her feet. She doesn't have a foothold in midair.
For a more gameplay valid reason: Because there's a reason she can't just fly or has a jetpack. She's already tied with Assault for most mobile class, she doesn't need the ability to basically fly on top of it.
Lunge is already way too good and needs to be reduced and you are asking for it to be better? It should not be possible to lunge-grapple, then lunge escape after the animation completes. One or the other yes, but not both. This would make attacks carry slightly higher risk to the assassin as they would not be more reliant on smoke bomb escape which has a significantly longer cooldown.
If you're being rung out as an assassin, chances are you did something very "Un-assassin" like, and there fore are about to be punished for it. Kind of like how Supports go all commando with the shotgun and get a good charge grapple out of the ring instead of staying in the comfort of their firebase.
Lunge and smoke bomb and dash already make her by far the most mobile class in the game. Assault is the only class that can even come CLOSE to comparing and even then he can only do it for extremely short bursts of time (and if he wants to gain the jump advantage assassin has with smoke bomb he has to sacrifice a portion of his health) Lunge has 2 second CD and charge has aprox 10second CD I'd say in terms of mobility altering strengths hover and dash are pretty much perfectly equal.