Needs some cloaking effect - the very very old Butterfly Knife had a nice cloaking effect, even if the backstab failed and worked outside of minigames.
Idea: Cloaking Player Type. Instead of jets, pressing the Jet key (pretty much taken as 'alternate fire' for everything) will cause you to turn invisible (+ name hiding) for the duration of a slowly regenerating cloak meter, displayed as jet fuel.