*You have a spring in your step.*
Your running window vaults are always fast vaults.
You are always Exhausted.
This would make already far too prevalent near-infinite window loops even more ridiculous, and unironically make the Z-wall jokes almost unironic. The ability to always fast vault was actually an ability Survivors had earlier in the game; I had the miserable experience of playing that version of this game too. Even in the form of a perk, unlimited fast vaults like this should not be.
However, your inclusion of "You are always exhausted" gave me an idea; perhaps the ability to turn a medium vault into a fast vault could be tied to a 30/25/20 second Exhaustion cooldown?
I agree with the 2nd guy permanent fast vaults is an extremely powerful thing even in exchange for no exhaustion perks which frankly you won't need with a perk like this maybe a new exhaustion perk instead since its just too strong in the right hands.