That's all very well, as long as there's no common modes of failure. Redundancy can be a means to achieve reliability, but not always. Imagine the cause of failure is a bug which kicks in at a specific time of day, or an integer overflow which happens after a certain amount of uptime, or all the motor drivers are susceptible to a specific RF frequency. It doesn't matter how many motors you have if they're all susceptible to the same failure mode.