I am not sure whether you are playing on PS4 or PC, but i do know that keybindings are stored in the Documents\My Games\Final Fantasy XIV - A Realm Reborn\KEYBIND.DAT file, would it not perhaps be possible to use an external program to keep copies of this file and then select them using say, a system tray icon when you want to switch jobs? The only caveat I foresee is that it may not load the keybinds if the game is already running and the file changes, which would mean a logout every time you wanted to change keybinds, or worse a restart of the game.