Two whole separate systems after the thermostat switch seems like a bit of overkill.
Electric fans most never die in a shorted condition, 99.9% they fail with an open field in which case the other fan would continue to run.
Lets get the guy functional, and he can mod things as he see's the need.
1 fuse blown or relay failed because 1 fan has a fault, both fans stop.
I cant/wont argue though. I take my clues from how these things are done in production vehicles. Factory engineers know a lot more about it than I do.
Go ask them. LOL
