Not exactly the same but some have tried a similar idea: KF-SwiftBoxyDeath from SwiftBrutalDeath comes to mind, and KF-CopyAndPaste from Mark-James did something similar, the latter uses a physicsvolume with low gravity however. Gameplay-wise I think it's roughly the same result and there's two main problems: 1 - head hitboxes might as well not exist when zeds are being accelerated vertically, 2 - zeds can't track players properly when players fly off.

Now this won't work in vanilla KF but if I were to do this I'd setup a gamemode with only flying enemies (Lost Soul, Maledict, Cacodemons etc), fill the map with FlyingPathnodes and put a classblocker over the trampolines so that only players can use them.