I like the idea of a two level trait, I'd suggest something like this :
Lvl 1 : instant swap with prepared, swapping to a weapon from inventory takes less time (lets say .5 sec instead of 1)
Lvl 2 : instant swap with any weapon, prepared or not, and some little bonus, like faster/instant equipping of ammo boxes and/or armors.
We could even imagine a 3rd level with instant use of any item in inventory (quite redundant with techie, ofc, but not everyone is techie)
Forgot to mention I hate the current system, where juggler is quite OP with correct keybindings. not intuitive, not balanced...