we always start the first engine on the S76A+ with the rotor brake on, and release it at 50%N1, also at shutdown stop the rotor on the rotor brake with one engine running at ground idle before shutting it down.
also we can bring both engines back to ground idle and stop the rotor on the rotor brake, and keep both engines running in certain situations like loading difficult freight on an offshore helideck when you really dont want to be shutting down unless you have to.
obviously you cant do either of these on a Jetbox, but assuming it doesnt break its tie down and you abort the start dont see what damage it can cause as it is a free turbine, am I wrong ?