There isn't a default keybind for Ctrl+E. You can't just have servers force a keybind on a client, you'd have to make it go through one of the existing functions, such as "Alt-Fire" on some guns with Jet or changing some weapon modes with "L". I'm suggesting the Use Paint command for "Medic!" in minigames as its default is E anyway, like in the game. You could use a /command outside of minigames to do the emote as well, sort of like the /alarm command and the button in Options for it.