I remembered this Latching power switch uses momentary pushbutton @ EDN circuit tatasal, which shouldn't work right without blocking diode given the electric motor load. But there are many other “MOSFET as switch” tutorials and articles, like this one @ ElectronicTutorials. You could use a small latching switch to control any MOSFET gate drive(s), and so you would be able to connect and disconnect the battery triggering a small switch which would drive the MOSFET(s) gate(s).