Cap, as an alternative to a blocking diode, what about installing a crowbar diode across the power leads? If power is hooked up in reverse, it goes through the crowbar and that appears to be a dead short, blowing the fuse in the power line to the light. Rashly assuming a proper fuse has been installed, of course. But it gets the voltage drop from a blocking diode out of the circuit. Or opens the whole can of worms on "protections".
I'd still suggest adding a chip (there must be cheap ones out there, because they are being used in really cheap flashlights) that would allow the light to strobe and SOS. Seen in LED flashlights shipping from China to the US for $5 each, including ground post shipping, so the chip can't cost more than what, one cheap LED does?