A most helpful idea is to have an "indication" circuit off the solenoid contacts to an indicator light on the panel. If the indicator light is on after starting, turn off the master switch and the engine........................ That is a valuable idea to let you know the starter is still engaged when you let go of the switch. However, since that wire that sends the signal is probably 22 Ga (5 amps) and the starter cables are capable of handling hundreds of amps, best to put a little blade fuse assembly in the small signal line so that if it were to short..... Think heat, smoke, and worse. Fred