Well since you expressed interest, I might as well go into the rest of my autism OC donut steel.
The whole vault attack wouldn't be her main power.
It would more so be a state to switch between like Doctor's Therapy and Treatment modes.
There would be a standard movement mode where you're movement is the same as a basic killer, complete with a break pallet option, though the break option is at a slower speed, as to encourage using your power.
The second state would be based around that she was in a gang or whatever, and would have hit targets.
At the start of a match, you're assigned a random survivor as a hit.
When you injure that survivor as well as down that survivor, it fills your hit meter.
When you hook them, it fills the meter a whole bunch, and switches your hit to a different survivor to repeat the cycle.
The hit meter is what allows you to use your vault attack mode, and when you activate it, it slowly drains it, kinda like EW.
You can switch back to standard movement whenever you want, and that will pause the drain.
That way you can't just start off super fast and shit all over everyone, and you need to be careful about how you manage your meter.
As for the lunge attack, it would stun you depending on your action.
standard window vault = no stun
pallet vault + no follow up action = very small stun
pallet vault + missed attack = medium stun
pallet vault + successful attack = large stun
I drew a picture of her a while back, and went for a trashy 90's gang look, but also wanted to include some Yakuza style shit, so I ended up giving her the classic creepy Japanese girl hair.
As for a replacement perk, I'm really not sure. I haven't thought much about it until just now.