If you do all of that the situation will never come up.
There are so many things to prepare for that creating an elaborate backup system for the water cooling would be just adding complexity to your system. You can run out of fuel and get air in the lines, have water or trash in the fuel, have a steering failure, a transmission linkage problem etc...
So I wouldn't focus on that one possible problem. Just keep the strainer clean. (and the seacock on
Twenty years from now you will be more disappointed by the things y%^&*.....oh never mind. 90% of the people on sailing forums already use that as their signature! I'm not a conformist.