Is it possible to have a gesture's action switch the active font?
I don't believe so.
To change fonts you must hold down the button and perform a STAB motion. Once in the menu you twist the saber (force move) to change to a different font.
To preform a gesture you start from the saber at idle. If you begin a self programmed gesture by holding down the button I'm pretty sure it would not allow the gesture to be programmed in the first place, Or it would just shut off the saber. Not switch to a new font.
If you go into the editing program on your computer and plug in the saber, you can uncheck the boxes on the gestures tab. That will turn off all gestures on that font. When you want to use the gestures again you can reprogram the gestures with new movements. You don't need to plug into a computer to program new movements.