I guess dangerous is a matter of opinion, some people jump out of planes for fun. The safety protocols i plan on having in place will allow the system to operate with a faulty module or will shut everything down in the event of a malfunction in the motor driver device. Also the reason why there is prototyping, small and moving to something large when proved viable.
Hey as for Arduino being reliable, i have a kureig water filler setup that has been running for almost 2 year never hiccuped once...
Oh and btw this is something different though still dealing with boats lol.