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In the commercial world of radio's (R/T) the Tait/Motorola/etc rigs have all sorts of "idiot proofing" built in....the most useful ones being FAST blow fuses or circuit breakers combined with a very large (>100 amp) suicide diode in the main power leads to remove power really, really fast in the event of a major problem.
Just remember, as soon as you make something "idiot-proof", nature will invent a better idiot...
A fuse and sacrificial diode are all very well, BUT.. Fuses take time to rupture, and a power transisistor always has, and always will be the fastest fuse on 3 legs... or 4 or whatever. For higher power items, I prefer the Idiot-Proofing method of a big relay!... Car accessory type of thing, in series with the input line, and the coil energized with a smaller diode!.. Wrong polarity, no coil current, so no power to item. It also has a zero volt-drop advantage. Smaller items are catered for with a SERIES diode, the 0.7V volt drop rarely has any effect on smaller items, as they tend to be internally regulated to lower voltages anyway.